diff --git a/json_serializable/CHANGELOG.md b/json_serializable/CHANGELOG.md
index fc5676b04..7e79368d3 100644
--- a/json_serializable/CHANGELOG.md
+++ b/json_serializable/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 6.3.0-dev
+
+- Added support for using a `JsonConverter<MyClass, Object>` on properties
+  of type `MyClass?`. ([#822](https://github.com/google/json_serializable.dart/issues/822))
+
 ## 6.2.0
 
 - Added support for the new `FieldRename.screamingSnake` field in
diff --git a/json_serializable/lib/src/type_helpers/json_converter_helper.dart b/json_serializable/lib/src/type_helpers/json_converter_helper.dart
index 8c0df9f3a..10fa483b4 100644
--- a/json_serializable/lib/src/type_helpers/json_converter_helper.dart
+++ b/json_serializable/lib/src/type_helpers/json_converter_helper.dart
@@ -32,6 +32,24 @@ class JsonConverterHelper extends TypeHelper {
       return null;
     }
 
+    if (!converter.fieldType.isNullableType && targetType.isNullableType) {
+      const converterToJsonName = r'_$JsonConverterToJson';
+      context.addMember('''
+Json? $converterToJsonName<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) => ${ifNullOrElse('value', 'null', 'toJson(value)')};
+''');
+
+      return _nullableJsonConverterLambdaResult(
+        converter,
+        name: converterToJsonName,
+        targetType: targetType,
+        expression: expression,
+        callback: '${converter.accessString}.toJson',
+      );
+    }
+
     return LambdaResult(expression, '${converter.accessString}.toJson');
   }
 
@@ -49,6 +67,24 @@ class JsonConverterHelper extends TypeHelper {
 
     final asContent = asStatement(converter.jsonType);
 
+    if (!converter.jsonType.isNullableType && targetType.isNullableType) {
+      const converterFromJsonName = r'_$JsonConverterFromJson';
+      context.addMember('''
+Value? $converterFromJsonName<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) => ${ifNullOrElse('json', 'null', 'fromJson(json as Json)')};
+''');
+
+      return _nullableJsonConverterLambdaResult(
+        converter,
+        name: converterFromJsonName,
+        targetType: targetType,
+        expression: expression,
+        callback: '${converter.accessString}.fromJson',
+      );
+    }
+
     return LambdaResult(
       expression,
       '${converter.accessString}.fromJson',
@@ -57,24 +93,51 @@ class JsonConverterHelper extends TypeHelper {
   }
 }
 
+String _nullableJsonConverterLambdaResult(
+  _JsonConvertData converter, {
+  required String name,
+  required DartType targetType,
+  required String expression,
+  required String callback,
+}) {
+  final jsonDisplayString = typeToCode(converter.jsonType);
+  final fieldTypeDisplayString = converter.isGeneric
+      ? typeToCode(targetType)
+      : typeToCode(converter.fieldType);
+
+  return '$name<$jsonDisplayString, $fieldTypeDisplayString>('
+      '$expression, $callback)';
+}
+
 class _JsonConvertData {
   final String accessString;
   final DartType jsonType;
+  final DartType fieldType;
+  final bool isGeneric;
 
   _JsonConvertData.className(
     String className,
     String accessor,
     this.jsonType,
-  ) : accessString = 'const $className${_withAccessor(accessor)}()';
+    this.fieldType,
+  )   : accessString = 'const $className${_withAccessor(accessor)}()',
+        isGeneric = false;
 
   _JsonConvertData.genericClass(
     String className,
     String genericTypeArg,
     String accessor,
     this.jsonType,
-  ) : accessString = '$className<$genericTypeArg>${_withAccessor(accessor)}()';
+    this.fieldType,
+  )   : accessString =
+            '$className<$genericTypeArg>${_withAccessor(accessor)}()',
+        isGeneric = true;
 
-  _JsonConvertData.propertyAccess(this.accessString, this.jsonType);
+  _JsonConvertData.propertyAccess(
+    this.accessString,
+    this.jsonType,
+    this.fieldType,
+  ) : isGeneric = false;
 
   static String _withAccessor(String accessor) =>
       accessor.isEmpty ? '' : '.$accessor';
@@ -127,7 +190,11 @@ _JsonConvertData? _typeConverterFrom(
       accessString = '${enclosing.name}.$accessString';
     }
 
-    return _JsonConvertData.propertyAccess(accessString, match.jsonType);
+    return _JsonConvertData.propertyAccess(
+      accessString,
+      match.jsonType,
+      match.fieldType,
+    );
   }
 
   final reviver = ConstantReader(match.annotation).revive();
@@ -145,6 +212,7 @@ _JsonConvertData? _typeConverterFrom(
       match.genericTypeArg!,
       reviver.accessor,
       match.jsonType,
+      match.fieldType,
     );
   }
 
@@ -152,11 +220,13 @@ _JsonConvertData? _typeConverterFrom(
     match.annotation.type!.element!.name!,
     reviver.accessor,
     match.jsonType,
+    match.fieldType,
   );
 }
 
 class _ConverterMatch {
   final DartObject annotation;
+  final DartType fieldType;
   final DartType jsonType;
   final ElementAnnotation elementAnnotation;
   final String? genericTypeArg;
@@ -166,6 +236,7 @@ class _ConverterMatch {
     this.annotation,
     this.jsonType,
     this.genericTypeArg,
+    this.fieldType,
   );
 }
 
@@ -191,9 +262,15 @@ _ConverterMatch? _compatibleMatch(
 
   final fieldType = jsonConverterSuper.typeArguments[0];
 
-  if (fieldType == targetType) {
+  // Allow assigning T to T?
+  if (fieldType == targetType || fieldType == targetType.promoteNonNullable()) {
     return _ConverterMatch(
-        annotation, constantValue, jsonConverterSuper.typeArguments[1], null);
+      annotation,
+      constantValue,
+      jsonConverterSuper.typeArguments[1],
+      null,
+      fieldType,
+    );
   }
 
   if (fieldType is TypeParameterType && targetType is TypeParameterType) {
@@ -212,6 +289,7 @@ _ConverterMatch? _compatibleMatch(
       constantValue,
       jsonConverterSuper.typeArguments[1],
       '${targetType.element.name}${targetType.isNullableType ? '?' : ''}',
+      fieldType,
     );
   }
 
diff --git a/json_serializable/pubspec.yaml b/json_serializable/pubspec.yaml
index 081f91ac1..00db66b4f 100644
--- a/json_serializable/pubspec.yaml
+++ b/json_serializable/pubspec.yaml
@@ -1,5 +1,5 @@
 name: json_serializable
-version: 6.2.0
+version: 6.3.0-dev
 description: >-
   Automatically generate code for converting to and from JSON by annotating
   Dart classes.
diff --git a/json_serializable/test/generic_files/generic_class.g.dart b/json_serializable/test/generic_files/generic_class.g.dart
index e45e840d4..c2f216483 100644
--- a/json_serializable/test/generic_files/generic_class.g.dart
+++ b/json_serializable/test/generic_files/generic_class.g.dart
@@ -39,10 +39,10 @@ GenericClassWithConverter<T, S>
           ..fieldObject = json['fieldObject']
           ..fieldDynamic = json['fieldDynamic']
           ..fieldInt = json['fieldInt'] as int?
-          ..fieldT = _SimpleConverter<T?>()
-              .fromJson(json['fieldT'] as Map<String, dynamic>)
-          ..fieldS = _SimpleConverter<S?>()
-              .fromJson(json['fieldS'] as Map<String, dynamic>)
+          ..fieldT = _$JsonConverterFromJson<Map<String, dynamic>, T>(
+              json['fieldT'], _SimpleConverter<T?>().fromJson)
+          ..fieldS = _$JsonConverterFromJson<Map<String, dynamic>, S>(
+              json['fieldS'], _SimpleConverter<S?>().fromJson)
           ..duration = const _DurationMillisecondConverter.named()
               .fromJson(json['duration'] as int?)
           ..listDuration = const _DurationListMillisecondConverter()
@@ -54,14 +54,28 @@ Map<String, dynamic> _$GenericClassWithConverterToJson<T extends num, S>(
       'fieldObject': instance.fieldObject,
       'fieldDynamic': instance.fieldDynamic,
       'fieldInt': instance.fieldInt,
-      'fieldT': _SimpleConverter<T?>().toJson(instance.fieldT),
-      'fieldS': _SimpleConverter<S?>().toJson(instance.fieldS),
+      'fieldT': _$JsonConverterToJson<Map<String, dynamic>, T>(
+          instance.fieldT, _SimpleConverter<T?>().toJson),
+      'fieldS': _$JsonConverterToJson<Map<String, dynamic>, S>(
+          instance.fieldS, _SimpleConverter<S?>().toJson),
       'duration':
           const _DurationMillisecondConverter.named().toJson(instance.duration),
       'listDuration': const _DurationListMillisecondConverter()
           .toJson(instance.listDuration),
     };
 
+Value? _$JsonConverterFromJson<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) =>
+    json == null ? null : fromJson(json as Json);
+
+Json? _$JsonConverterToJson<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) =>
+    value == null ? null : toJson(value);
+
 Issue980ParentClass _$Issue980ParentClassFromJson(Map<String, dynamic> json) =>
     Issue980ParentClass(
       (json['list'] as List<dynamic>)
diff --git a/json_serializable/test/json_serializable_test.dart b/json_serializable/test/json_serializable_test.dart
index 9d29fce0b..ef5e38e01 100644
--- a/json_serializable/test/json_serializable_test.dart
+++ b/json_serializable/test/json_serializable_test.dart
@@ -85,6 +85,7 @@ const _expectedAnnotatedTests = {
   'JsonConverterCtorParams',
   'JsonConverterDuplicateAnnotations',
   'JsonConverterNamedCtor',
+  'JsonConverterNullableToNonNullable',
   'JsonConverterOnGetter',
   'JsonConverterWithBadTypeArg',
   'JsonValueValid',
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.dart b/json_serializable/test/kitchen_sink/kitchen_sink.dart
index 92bd1c94d..4eabab0e2 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.dart
@@ -66,9 +66,13 @@ class _Factory implements k.KitchenSinkFactory<String, dynamic> {
         [],
         BigInt.zero,
         {},
+        BigInt.zero,
+        {},
         TrivialNumber(0),
         {},
         DateTime.fromMillisecondsSinceEpoch(0),
+        TrivialNumber(0),
+        {},
       );
 
   k.JsonConverterTestClass jsonConverterFromJson(Map<String, dynamic> json) =>
@@ -203,9 +207,13 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
     this.durationList,
     this.bigInt,
     this.bigIntMap,
+    this.nullableBigInt,
+    this.nullableBigIntMap,
     this.numberSilly,
     this.numberSillySet,
     this.dateTime,
+    this.nullableNumberSilly,
+    this.nullableNumberSillySet,
   );
 
   factory JsonConverterTestClass.fromJson(Map<String, dynamic> json) =>
@@ -219,10 +227,16 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
   BigInt bigInt;
   Map<String, BigInt> bigIntMap;
 
+  BigInt? nullableBigInt;
+  Map<String, BigInt?> nullableBigIntMap;
+
   TrivialNumber numberSilly;
   Set<TrivialNumber> numberSillySet;
 
   DateTime? dateTime;
+
+  TrivialNumber? nullableNumberSilly;
+  Set<TrivialNumber?> nullableNumberSillySet;
 }
 
 @JsonSerializable()
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g.dart
index ec7fa097c..c74f6aee0 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g.dart
@@ -146,11 +146,24 @@ JsonConverterTestClass _$JsonConverterTestClassFromJson(
         (k, e) =>
             MapEntry(k, const BigIntStringConverter().fromJson(e as String)),
       ),
+      _$JsonConverterFromJson<String, BigInt>(
+          json['nullableBigInt'], const BigIntStringConverter().fromJson),
+      (json['nullableBigIntMap'] as Map<String, dynamic>).map(
+        (k, e) => MapEntry(
+            k,
+            _$JsonConverterFromJson<String, BigInt>(
+                e, const BigIntStringConverter().fromJson)),
+      ),
       TrivialNumberConverter.instance.fromJson(json['numberSilly'] as int?),
       (json['numberSillySet'] as List<dynamic>)
           .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
           .toSet(),
       const EpochDateTimeConverter().fromJson(json['dateTime'] as int?),
+      TrivialNumberConverter.instance
+          .fromJson(json['nullableNumberSilly'] as int?),
+      (json['nullableNumberSillySet'] as List<dynamic>)
+          .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
+          .toSet(),
     );
 
 Map<String, dynamic> _$JsonConverterTestClassToJson(
@@ -162,14 +175,38 @@ Map<String, dynamic> _$JsonConverterTestClassToJson(
       'bigInt': const BigIntStringConverter().toJson(instance.bigInt),
       'bigIntMap': instance.bigIntMap
           .map((k, e) => MapEntry(k, const BigIntStringConverter().toJson(e))),
+      'nullableBigInt': _$JsonConverterToJson<String, BigInt>(
+          instance.nullableBigInt, const BigIntStringConverter().toJson),
+      'nullableBigIntMap': instance.nullableBigIntMap.map((k, e) => MapEntry(
+          k,
+          _$JsonConverterToJson<String, BigInt>(
+              e, const BigIntStringConverter().toJson))),
       'numberSilly':
           TrivialNumberConverter.instance.toJson(instance.numberSilly),
       'numberSillySet': instance.numberSillySet
           .map(TrivialNumberConverter.instance.toJson)
           .toList(),
       'dateTime': const EpochDateTimeConverter().toJson(instance.dateTime),
+      'nullableNumberSilly': _$JsonConverterToJson<int?, TrivialNumber>(
+          instance.nullableNumberSilly, TrivialNumberConverter.instance.toJson),
+      'nullableNumberSillySet': instance.nullableNumberSillySet
+          .map((e) => _$JsonConverterToJson<int?, TrivialNumber>(
+              e, TrivialNumberConverter.instance.toJson))
+          .toList(),
     };
 
+Value? _$JsonConverterFromJson<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) =>
+    json == null ? null : fromJson(json as Json);
+
+Json? _$JsonConverterToJson<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) =>
+    value == null ? null : toJson(value);
+
 JsonConverterGeneric<S, T, U> _$JsonConverterGenericFromJson<S, T, U>(
         Map<String, dynamic> json) =>
     JsonConverterGeneric<S, T, U>(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.dart
index bf82df50d..9da91757a 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.dart
@@ -65,9 +65,13 @@ class _Factory implements k.KitchenSinkFactory<dynamic, dynamic> {
         [],
         BigInt.zero,
         {},
+        BigInt.zero,
+        {},
         TrivialNumber(0),
         {},
         DateTime.fromMillisecondsSinceEpoch(0),
+        TrivialNumber(0),
+        {},
       );
 
   k.JsonConverterTestClass jsonConverterFromJson(Map<String, dynamic> json) =>
@@ -205,9 +209,13 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
     this.durationList,
     this.bigInt,
     this.bigIntMap,
+    this.nullableBigInt,
+    this.nullableBigIntMap,
     this.numberSilly,
     this.numberSillySet,
     this.dateTime,
+    this.nullableNumberSilly,
+    this.nullableNumberSillySet,
   );
 
   factory JsonConverterTestClass.fromJson(Map<String, dynamic> json) =>
@@ -221,10 +229,16 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
   BigInt bigInt;
   Map<String, BigInt> bigIntMap;
 
+  BigInt? nullableBigInt;
+  Map<String, BigInt?> nullableBigIntMap;
+
   TrivialNumber numberSilly;
   Set<TrivialNumber> numberSillySet;
 
   DateTime? dateTime;
+
+  TrivialNumber? nullableNumberSilly;
+  Set<TrivialNumber?> nullableNumberSillySet;
 }
 
 @JsonSerializable(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.g.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.g.dart
index 16d995c98..638091dcc 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.g.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map.g.dart
@@ -137,11 +137,24 @@ JsonConverterTestClass _$JsonConverterTestClassFromJson(Map json) =>
         (k, e) => MapEntry(
             k as String, const BigIntStringConverter().fromJson(e as String)),
       ),
+      _$JsonConverterFromJson<String, BigInt>(
+          json['nullableBigInt'], const BigIntStringConverter().fromJson),
+      (json['nullableBigIntMap'] as Map).map(
+        (k, e) => MapEntry(
+            k as String,
+            _$JsonConverterFromJson<String, BigInt>(
+                e, const BigIntStringConverter().fromJson)),
+      ),
       TrivialNumberConverter.instance.fromJson(json['numberSilly'] as int?),
       (json['numberSillySet'] as List<dynamic>)
           .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
           .toSet(),
       const EpochDateTimeConverter().fromJson(json['dateTime'] as int?),
+      TrivialNumberConverter.instance
+          .fromJson(json['nullableNumberSilly'] as int?),
+      (json['nullableNumberSillySet'] as List<dynamic>)
+          .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
+          .toSet(),
     );
 
 Map<String, dynamic> _$JsonConverterTestClassToJson(
@@ -153,14 +166,38 @@ Map<String, dynamic> _$JsonConverterTestClassToJson(
       'bigInt': const BigIntStringConverter().toJson(instance.bigInt),
       'bigIntMap': instance.bigIntMap
           .map((k, e) => MapEntry(k, const BigIntStringConverter().toJson(e))),
+      'nullableBigInt': _$JsonConverterToJson<String, BigInt>(
+          instance.nullableBigInt, const BigIntStringConverter().toJson),
+      'nullableBigIntMap': instance.nullableBigIntMap.map((k, e) => MapEntry(
+          k,
+          _$JsonConverterToJson<String, BigInt>(
+              e, const BigIntStringConverter().toJson))),
       'numberSilly':
           TrivialNumberConverter.instance.toJson(instance.numberSilly),
       'numberSillySet': instance.numberSillySet
           .map(TrivialNumberConverter.instance.toJson)
           .toList(),
       'dateTime': const EpochDateTimeConverter().toJson(instance.dateTime),
+      'nullableNumberSilly': _$JsonConverterToJson<int?, TrivialNumber>(
+          instance.nullableNumberSilly, TrivialNumberConverter.instance.toJson),
+      'nullableNumberSillySet': instance.nullableNumberSillySet
+          .map((e) => _$JsonConverterToJson<int?, TrivialNumber>(
+              e, TrivialNumberConverter.instance.toJson))
+          .toList(),
     };
 
+Value? _$JsonConverterFromJson<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) =>
+    json == null ? null : fromJson(json as Json);
+
+Json? _$JsonConverterToJson<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) =>
+    value == null ? null : toJson(value);
+
 JsonConverterGeneric<S, T, U> _$JsonConverterGenericFromJson<S, T, U>(
         Map json) =>
     JsonConverterGeneric<S, T, U>(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.dart
index 0a5119aa5..71812ba2e 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.dart
@@ -65,9 +65,13 @@ class _Factory implements k.KitchenSinkFactory<dynamic, dynamic> {
         [],
         BigInt.zero,
         {},
+        BigInt.zero,
+        {},
         TrivialNumber(0),
         {},
         DateTime.fromMillisecondsSinceEpoch(0),
+        TrivialNumber(0),
+        {},
       );
 
   k.JsonConverterTestClass jsonConverterFromJson(Map<String, dynamic> json) =>
@@ -207,9 +211,13 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
     this.durationList,
     this.bigInt,
     this.bigIntMap,
+    this.nullableBigInt,
+    this.nullableBigIntMap,
     this.numberSilly,
     this.numberSillySet,
     this.dateTime,
+    this.nullableNumberSilly,
+    this.nullableNumberSillySet,
   );
 
   factory JsonConverterTestClass.fromJson(Map<String, dynamic> json) =>
@@ -223,10 +231,16 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
   BigInt bigInt;
   Map<String, BigInt> bigIntMap;
 
+  BigInt? nullableBigInt;
+  Map<String, BigInt?> nullableBigIntMap;
+
   TrivialNumber numberSilly;
   Set<TrivialNumber> numberSillySet;
 
   DateTime? dateTime;
+
+  TrivialNumber? nullableNumberSilly;
+  Set<TrivialNumber?> nullableNumberSillySet;
 }
 
 @JsonSerializable(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.g.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.g.dart
index 8be98d6cb..1d8c4c26b 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.g.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_any_map__checked.g.dart
@@ -198,6 +198,18 @@ JsonConverterTestClass _$JsonConverterTestClassFromJson(Map json) =>
                     (k, e) => MapEntry(k as String,
                         const BigIntStringConverter().fromJson(e as String)),
                   )),
+          $checkedConvert(
+              'nullableBigInt',
+              (v) => _$JsonConverterFromJson<String, BigInt>(
+                  v, const BigIntStringConverter().fromJson)),
+          $checkedConvert(
+              'nullableBigIntMap',
+              (v) => (v as Map).map(
+                    (k, e) => MapEntry(
+                        k as String,
+                        _$JsonConverterFromJson<String, BigInt>(
+                            e, const BigIntStringConverter().fromJson)),
+                  )),
           $checkedConvert('numberSilly',
               (v) => TrivialNumberConverter.instance.fromJson(v as int?)),
           $checkedConvert(
@@ -208,6 +220,14 @@ JsonConverterTestClass _$JsonConverterTestClassFromJson(Map json) =>
                   .toSet()),
           $checkedConvert('dateTime',
               (v) => const EpochDateTimeConverter().fromJson(v as int?)),
+          $checkedConvert('nullableNumberSilly',
+              (v) => TrivialNumberConverter.instance.fromJson(v as int?)),
+          $checkedConvert(
+              'nullableNumberSillySet',
+              (v) => (v as List<dynamic>)
+                  .map((e) =>
+                      TrivialNumberConverter.instance.fromJson(e as int?))
+                  .toSet()),
         );
         return val;
       },
@@ -222,14 +242,38 @@ Map<String, dynamic> _$JsonConverterTestClassToJson(
       'bigInt': const BigIntStringConverter().toJson(instance.bigInt),
       'bigIntMap': instance.bigIntMap
           .map((k, e) => MapEntry(k, const BigIntStringConverter().toJson(e))),
+      'nullableBigInt': _$JsonConverterToJson<String, BigInt>(
+          instance.nullableBigInt, const BigIntStringConverter().toJson),
+      'nullableBigIntMap': instance.nullableBigIntMap.map((k, e) => MapEntry(
+          k,
+          _$JsonConverterToJson<String, BigInt>(
+              e, const BigIntStringConverter().toJson))),
       'numberSilly':
           TrivialNumberConverter.instance.toJson(instance.numberSilly),
       'numberSillySet': instance.numberSillySet
           .map(TrivialNumberConverter.instance.toJson)
           .toList(),
       'dateTime': const EpochDateTimeConverter().toJson(instance.dateTime),
+      'nullableNumberSilly': _$JsonConverterToJson<int?, TrivialNumber>(
+          instance.nullableNumberSilly, TrivialNumberConverter.instance.toJson),
+      'nullableNumberSillySet': instance.nullableNumberSillySet
+          .map((e) => _$JsonConverterToJson<int?, TrivialNumber>(
+              e, TrivialNumberConverter.instance.toJson))
+          .toList(),
     };
 
+Value? _$JsonConverterFromJson<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) =>
+    json == null ? null : fromJson(json as Json);
+
+Json? _$JsonConverterToJson<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) =>
+    value == null ? null : toJson(value);
+
 JsonConverterGeneric<S, T, U> _$JsonConverterGenericFromJson<S, T, U>(
         Map json) =>
     $checkedCreate(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.dart
index 5927b1aaa..a8fd5e1d8 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.dart
@@ -66,9 +66,13 @@ class _Factory implements k.KitchenSinkFactory<String, dynamic> {
         [],
         BigInt.zero,
         {},
+        BigInt.zero,
+        {},
         TrivialNumber(0),
         {},
         DateTime.fromMillisecondsSinceEpoch(0),
+        TrivialNumber(0),
+        {},
       );
 
   k.JsonConverterTestClass jsonConverterFromJson(Map<String, dynamic> json) =>
@@ -207,9 +211,13 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
     this.durationList,
     this.bigInt,
     this.bigIntMap,
+    this.nullableBigInt,
+    this.nullableBigIntMap,
     this.numberSilly,
     this.numberSillySet,
     this.dateTime,
+    this.nullableNumberSilly,
+    this.nullableNumberSillySet,
   );
 
   factory JsonConverterTestClass.fromJson(Map<String, dynamic> json) =>
@@ -223,10 +231,16 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
   BigInt bigInt;
   Map<String, BigInt> bigIntMap;
 
+  BigInt? nullableBigInt;
+  Map<String, BigInt?> nullableBigIntMap;
+
   TrivialNumber numberSilly;
   Set<TrivialNumber> numberSillySet;
 
   DateTime? dateTime;
+
+  TrivialNumber? nullableNumberSilly;
+  Set<TrivialNumber?> nullableNumberSillySet;
 }
 
 @JsonSerializable(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.g.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.g.dart
index 6afeb29a2..a0246e8bc 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.g.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_exclude_null.g.dart
@@ -154,11 +154,24 @@ JsonConverterTestClass _$JsonConverterTestClassFromJson(
         (k, e) =>
             MapEntry(k, const BigIntStringConverter().fromJson(e as String)),
       ),
+      _$JsonConverterFromJson<String, BigInt>(
+          json['nullableBigInt'], const BigIntStringConverter().fromJson),
+      (json['nullableBigIntMap'] as Map<String, dynamic>).map(
+        (k, e) => MapEntry(
+            k,
+            _$JsonConverterFromJson<String, BigInt>(
+                e, const BigIntStringConverter().fromJson)),
+      ),
       TrivialNumberConverter.instance.fromJson(json['numberSilly'] as int?),
       (json['numberSillySet'] as List<dynamic>)
           .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
           .toSet(),
       const EpochDateTimeConverter().fromJson(json['dateTime'] as int?),
+      TrivialNumberConverter.instance
+          .fromJson(json['nullableNumberSilly'] as int?),
+      (json['nullableNumberSillySet'] as List<dynamic>)
+          .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
+          .toSet(),
     );
 
 Map<String, dynamic> _$JsonConverterTestClassToJson(
@@ -177,6 +190,14 @@ Map<String, dynamic> _$JsonConverterTestClassToJson(
   writeNotNull('bigInt', const BigIntStringConverter().toJson(instance.bigInt));
   val['bigIntMap'] = instance.bigIntMap
       .map((k, e) => MapEntry(k, const BigIntStringConverter().toJson(e)));
+  writeNotNull(
+      'nullableBigInt',
+      _$JsonConverterToJson<String, BigInt>(
+          instance.nullableBigInt, const BigIntStringConverter().toJson));
+  val['nullableBigIntMap'] = instance.nullableBigIntMap.map((k, e) => MapEntry(
+      k,
+      _$JsonConverterToJson<String, BigInt>(
+          e, const BigIntStringConverter().toJson)));
   writeNotNull('numberSilly',
       TrivialNumberConverter.instance.toJson(instance.numberSilly));
   val['numberSillySet'] = instance.numberSillySet
@@ -184,9 +205,29 @@ Map<String, dynamic> _$JsonConverterTestClassToJson(
       .toList();
   writeNotNull(
       'dateTime', const EpochDateTimeConverter().toJson(instance.dateTime));
+  writeNotNull(
+      'nullableNumberSilly',
+      _$JsonConverterToJson<int?, TrivialNumber>(instance.nullableNumberSilly,
+          TrivialNumberConverter.instance.toJson));
+  val['nullableNumberSillySet'] = instance.nullableNumberSillySet
+      .map((e) => _$JsonConverterToJson<int?, TrivialNumber>(
+          e, TrivialNumberConverter.instance.toJson))
+      .toList();
   return val;
 }
 
+Value? _$JsonConverterFromJson<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) =>
+    json == null ? null : fromJson(json as Json);
+
+Json? _$JsonConverterToJson<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) =>
+    value == null ? null : toJson(value);
+
 JsonConverterGeneric<S, T, U> _$JsonConverterGenericFromJson<S, T, U>(
         Map<String, dynamic> json) =>
     JsonConverterGeneric<S, T, U>(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.dart
index bce55d5f0..f5f13fc7d 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.dart
@@ -66,9 +66,13 @@ class _Factory implements k.KitchenSinkFactory<String, dynamic> {
         [],
         BigInt.zero,
         {},
+        BigInt.zero,
+        {},
         TrivialNumber(0),
         {},
         DateTime.fromMillisecondsSinceEpoch(0),
+        TrivialNumber(0),
+        {},
       );
 
   k.JsonConverterTestClass jsonConverterFromJson(Map<String, dynamic> json) =>
@@ -207,9 +211,13 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
     this.durationList,
     this.bigInt,
     this.bigIntMap,
+    this.nullableBigInt,
+    this.nullableBigIntMap,
     this.numberSilly,
     this.numberSillySet,
     this.dateTime,
+    this.nullableNumberSilly,
+    this.nullableNumberSillySet,
   );
 
   factory JsonConverterTestClass.fromJson(Map<String, dynamic> json) =>
@@ -223,10 +231,16 @@ class JsonConverterTestClass implements k.JsonConverterTestClass {
   BigInt bigInt;
   Map<String, BigInt> bigIntMap;
 
+  BigInt? nullableBigInt;
+  Map<String, BigInt?> nullableBigIntMap;
+
   TrivialNumber numberSilly;
   Set<TrivialNumber> numberSillySet;
 
   DateTime? dateTime;
+
+  TrivialNumber? nullableNumberSilly;
+  Set<TrivialNumber?> nullableNumberSillySet;
 }
 
 @JsonSerializable(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.g.dart b/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.g.dart
index cb0415623..e6f218fa6 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.g.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink.g_explicit_to_json.g.dart
@@ -148,11 +148,24 @@ JsonConverterTestClass _$JsonConverterTestClassFromJson(
         (k, e) =>
             MapEntry(k, const BigIntStringConverter().fromJson(e as String)),
       ),
+      _$JsonConverterFromJson<String, BigInt>(
+          json['nullableBigInt'], const BigIntStringConverter().fromJson),
+      (json['nullableBigIntMap'] as Map<String, dynamic>).map(
+        (k, e) => MapEntry(
+            k,
+            _$JsonConverterFromJson<String, BigInt>(
+                e, const BigIntStringConverter().fromJson)),
+      ),
       TrivialNumberConverter.instance.fromJson(json['numberSilly'] as int?),
       (json['numberSillySet'] as List<dynamic>)
           .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
           .toSet(),
       const EpochDateTimeConverter().fromJson(json['dateTime'] as int?),
+      TrivialNumberConverter.instance
+          .fromJson(json['nullableNumberSilly'] as int?),
+      (json['nullableNumberSillySet'] as List<dynamic>)
+          .map((e) => TrivialNumberConverter.instance.fromJson(e as int?))
+          .toSet(),
     );
 
 Map<String, dynamic> _$JsonConverterTestClassToJson(
@@ -164,14 +177,38 @@ Map<String, dynamic> _$JsonConverterTestClassToJson(
       'bigInt': const BigIntStringConverter().toJson(instance.bigInt),
       'bigIntMap': instance.bigIntMap
           .map((k, e) => MapEntry(k, const BigIntStringConverter().toJson(e))),
+      'nullableBigInt': _$JsonConverterToJson<String, BigInt>(
+          instance.nullableBigInt, const BigIntStringConverter().toJson),
+      'nullableBigIntMap': instance.nullableBigIntMap.map((k, e) => MapEntry(
+          k,
+          _$JsonConverterToJson<String, BigInt>(
+              e, const BigIntStringConverter().toJson))),
       'numberSilly':
           TrivialNumberConverter.instance.toJson(instance.numberSilly),
       'numberSillySet': instance.numberSillySet
           .map(TrivialNumberConverter.instance.toJson)
           .toList(),
       'dateTime': const EpochDateTimeConverter().toJson(instance.dateTime),
+      'nullableNumberSilly': _$JsonConverterToJson<int?, TrivialNumber>(
+          instance.nullableNumberSilly, TrivialNumberConverter.instance.toJson),
+      'nullableNumberSillySet': instance.nullableNumberSillySet
+          .map((e) => _$JsonConverterToJson<int?, TrivialNumber>(
+              e, TrivialNumberConverter.instance.toJson))
+          .toList(),
     };
 
+Value? _$JsonConverterFromJson<Json, Value>(
+  Object? json,
+  Value? Function(Json json) fromJson,
+) =>
+    json == null ? null : fromJson(json as Json);
+
+Json? _$JsonConverterToJson<Json, Value>(
+  Value? value,
+  Json? Function(Value value) toJson,
+) =>
+    value == null ? null : toJson(value);
+
 JsonConverterGeneric<S, T, U> _$JsonConverterGenericFromJson<S, T, U>(
         Map<String, dynamic> json) =>
     JsonConverterGeneric<S, T, U>(
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink_interface.dart b/json_serializable/test/kitchen_sink/kitchen_sink_interface.dart
index f69ade258..9f8740943 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink_interface.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink_interface.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../test_utils.dart';
+import 'json_converters.dart';
 import 'simple_object.dart';
 
 /// A key name that requires special encoding
@@ -41,6 +42,8 @@ abstract class KitchenSinkFactory<K, V> {
 }
 
 abstract class JsonConverterTestClass {
+  TrivialNumber? nullableNumberSilly;
+
   Map<String, dynamic> toJson();
 }
 
diff --git a/json_serializable/test/kitchen_sink/kitchen_sink_test.dart b/json_serializable/test/kitchen_sink/kitchen_sink_test.dart
index 8044c29d7..99e45bf40 100644
--- a/json_serializable/test/kitchen_sink/kitchen_sink_test.dart
+++ b/json_serializable/test/kitchen_sink/kitchen_sink_test.dart
@@ -6,6 +6,7 @@ import 'package:json_annotation/json_annotation.dart';
 import 'package:test/test.dart';
 
 import '../test_utils.dart';
+import 'json_converters.dart';
 import 'kitchen_sink.factories.dart';
 import 'kitchen_sink_interface.dart';
 import 'kitchen_sink_test_shared.dart';
@@ -54,10 +55,14 @@ const _jsonConverterValidValues = {
   'duration': 5,
   'durationList': [5],
   'bigInt': '5',
-  'bigIntMap': {'vaule': '5'},
+  'bigIntMap': {'value': '5'},
   'numberSilly': 5,
   'numberSillySet': [5],
-  'dateTime': 5
+  'dateTime': 5,
+  'nullableNumberSilly': 5,
+  'nullableBigInt': '42',
+  'nullableBigIntMap': {'value': '42'},
+  'nullableNumberSillySet': [42],
 };
 
 void _nonNullableTests(KitchenSinkFactory factory) {
@@ -96,9 +101,13 @@ void _nullableTests(KitchenSinkFactory factory) {
       'durationList': [],
       'bigInt': '0',
       'bigIntMap': {},
+      'nullableBigInt': '0',
+      'nullableBigIntMap': {},
       'numberSilly': 0,
       'numberSillySet': [],
-      'dateTime': 0
+      'dateTime': 0,
+      'nullableNumberSilly': 0,
+      'nullableNumberSillySet': [],
     });
 
     expect(json.keys, unorderedEquals(_jsonConverterValidValues.keys));
@@ -183,6 +192,18 @@ void _sharedTests(KitchenSinkFactory factory) {
     roundTripObject(item, factory.fromJson);
   });
 
+  test('JsonConverters with nullable JSON keys handle `null` JSON values', () {
+    final item = factory.jsonConverterFromJson({
+      ..._jsonConverterValidValues,
+      'nullableNumberSilly': null,
+    });
+
+    expect(
+      item.nullableNumberSilly,
+      isA<TrivialNumber>().having((e) => e.value, 'value', isNull),
+    );
+  });
+
   test('list and map of DateTime - not null', () {
     final now = DateTime.now();
     final item = factory.ctor(dateTimeIterable: <DateTime>[now])
diff --git a/json_serializable/test/src/json_converter_test_input.dart b/json_serializable/test/src/json_converter_test_input.dart
index 10d029b41..fbe7da28c 100644
--- a/json_serializable/test/src/json_converter_test_input.dart
+++ b/json_serializable/test/src/json_converter_test_input.dart
@@ -189,3 +189,25 @@ class _NeedsConversionConverter
   @override
   int toJson(_NeedsConversion object) => 0;
 }
+
+@ShouldThrow(
+  '''
+Could not generate `fromJson` code for `value`.
+To support the type `_NeedsConversion` you can:
+$converterOrKeyInstructions''',
+)
+@_NullableConverter()
+@JsonSerializable()
+class JsonConverterNullableToNonNullable {
+  late _NeedsConversion value;
+}
+
+class _NullableConverter implements JsonConverter<_NeedsConversion?, Object?> {
+  const _NullableConverter();
+
+  @override
+  _NeedsConversion? fromJson(Object? json) => null;
+
+  @override
+  Object? toJson(_NeedsConversion? object) => null;
+}