diff --git a/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php b/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php
index 8317b28b193..2363f77dd10 100644
--- a/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php
+++ b/src/Psalm/Internal/Type/Comparator/UnionTypeComparator.php
@@ -13,6 +13,7 @@
 use Psalm\Type\Atomic\TNull;
 use Psalm\Type\Atomic\TNumeric;
 use Psalm\Type\Atomic\TTemplateParam;
+use Psalm\Type\Atomic\TTypeAlias;
 
 use function array_merge;
 
@@ -59,7 +60,7 @@ public static function isContainedBy(
 
         $container_has_template = $container_type->hasTemplateOrStatic();
 
-        $input_atomic_types = \array_reverse($input_type->getAtomicTypes());
+        $input_atomic_types = \array_reverse(self::getTypeParts($codebase, $input_type));
 
         while ($input_type_part = \array_pop($input_atomic_types)) {
             if ($input_type_part instanceof TNull && $ignore_null) {
@@ -134,7 +135,7 @@ public static function isContainedBy(
                 }
             }
 
-            foreach ($container_type->getAtomicTypes() as $container_type_part) {
+            foreach (self::getTypeParts($codebase, $container_type) as $container_type_part) {
                 if ($ignore_null
                     && $container_type_part instanceof TNull
                     && !$input_type_part instanceof TNull
@@ -469,4 +470,37 @@ public static function canExpressionTypesBeIdentical(
 
         return false;
     }
+
+    /**
+     * @return list<Type\Atomic>
+     */
+    private static function getTypeParts(
+        Codebase $codebase,
+        Type\Union $union_type
+    ): array {
+        $atomic_types = [];
+        foreach ($union_type->getAtomicTypes() as $atomic_type) {
+            if (!$atomic_type instanceof TTypeAlias) {
+                \array_push($atomic_types, $atomic_type);
+                continue;
+            }
+            $expanded = TypeExpander::expandAtomic(
+                $codebase,
+                $atomic_type,
+                $atomic_type->declaring_fq_classlike_name,
+                $atomic_type->declaring_fq_classlike_name,
+                null,
+                true,
+                true
+            );
+            if ($expanded instanceof Type\Atomic) {
+                \array_push($atomic_types, $expanded);
+                continue;
+            }
+
+            \array_push($atomic_types, ...$expanded);
+        }
+
+        return $atomic_types;
+    }
 }
diff --git a/tests/TypeAnnotationTest.php b/tests/TypeAnnotationTest.php
index 8c3b23367b6..fb7ff764d6b 100644
--- a/tests/TypeAnnotationTest.php
+++ b/tests/TypeAnnotationTest.php
@@ -426,6 +426,25 @@ class B {}
                      */
                     class C implements A {}',
             ],
+            'importedTypeAliasAsConstrainedTypeParameterForImplementation' => [
+                '<?php
+                    namespace Bar;
+
+                    /** @template T of string */
+                    interface A {}
+
+                    /**
+                     * @psalm-type Foo = "foo"
+                     */
+                    class B {}
+
+                    /**
+                     * @psalm-import-type Foo from B
+                     * @implements A<Foo>
+                     */
+                    class C implements A {}
+                '
+            ],
             'importedTypeAliasAsTypeParameterForExtendedClass' => [
                 '<?php
                     namespace Bar;