diff --git a/dist-raw/node-cjs-loader-utils.js b/dist-raw/node-cjs-loader-utils.js
index b7ec0d531..8ddeca084 100644
--- a/dist-raw/node-cjs-loader-utils.js
+++ b/dist-raw/node-cjs-loader-utils.js
@@ -23,6 +23,8 @@ function assertScriptCanLoadAsCJSImpl(service, module, filename) {
   const tsNodeClassification = service.moduleTypeClassifier.classifyModule(normalizeSlashes(filename));
   if(tsNodeClassification.moduleType === 'cjs') return;
 
+  // TODO modify to ignore package.json when file extension is ESM-only
+
   // Function require shouldn't be used in ES modules.
   if (tsNodeClassification.moduleType === 'esm' || (pkg && pkg.data && pkg.data.type === 'module')) {
     const parentPath = module.parent && module.parent.filename;
diff --git a/dist-raw/node-esm-resolve-implementation.js b/dist-raw/node-esm-resolve-implementation.js
index 04ea84668..ce2ffad16 100644
--- a/dist-raw/node-esm-resolve-implementation.js
+++ b/dist-raw/node-esm-resolve-implementation.js
@@ -330,11 +330,19 @@ function resolveExtensions(search) {
  * TS's resolver can resolve foo.js to foo.ts, by replacing .js extension with several source extensions.
  * IMPORTANT: preserve ordering according to preferTsExts; this affects resolution behavior!
  */
-const replacementExtensions = extensions.filter(ext => ['.js', '.jsx', '.ts', '.tsx'].includes(ext));
+const replacementExtensionsForJs = extensions.filter(ext => ['.js', '.jsx', '.ts', '.tsx'].includes(ext));
+const replacementExtensionsForMjs = extensions.filter(ext => ['.mjs', '.mts'].includes(ext));
+const replacementExtensionsForCjs = extensions.filter(ext => ['.cjs', '.cts'].includes(ext));
 
 function resolveReplacementExtensions(search) {
-  if (search.pathname.match(/\.js$/)) {
-    const pathnameWithoutExtension = search.pathname.slice(0, search.pathname.length - 3);
+  const lastDotIndex = search.pathname.lastIndexOf('.');
+  const ext = search.pathname.slice(lastDotIndex);
+  if (ext === '.js' || ext === '.cjs' || ext === '.mjs') {
+    const pathnameWithoutExtension = search.pathname.slice(0, lastDotIndex);
+    const replacementExtensions =
+      ext === '.js' ? replacementExtensionsForJs
+      : ext === '.mjs' ? replacementExtensionsForMjs
+      : replacementExtensionsForCjs;
     for (let i = 0; i < replacementExtensions.length; i++) {
       const extension = replacementExtensions[i];
       const guess = new URL(search.toString());
diff --git a/src/esm.ts b/src/esm.ts
index c83fd22c4..f95987231 100644
--- a/src/esm.ts
+++ b/src/esm.ts
@@ -96,7 +96,7 @@ export function createEsmHooks(tsNodeService: Service) {
 
   // Custom implementation that considers additional file extensions and automatically adds file extensions
   const nodeResolveImplementation = createResolve({
-    ...getExtensions(tsNodeService.config),
+    ...tsNodeService.extensions,
     preferTsExts: tsNodeService.options.preferTsExts,
   });
 
@@ -112,7 +112,6 @@ export function createEsmHooks(tsNodeService: Service) {
   const hooksAPI: NodeLoaderHooksAPI1 | NodeLoaderHooksAPI2 = newHooksAPI
     ? { resolve, load, getFormat: undefined, transformSource: undefined }
     : { resolve, getFormat, transformSource, load: undefined };
-  return hooksAPI;
 
   function isFileUrlOrNodeStyleSpecifier(parsed: UrlWithStringQuery) {
     // We only understand file:// URLs, but in node, the specifier can be a node-style `./foo` or `foo`
@@ -205,6 +204,16 @@ export function createEsmHooks(tsNodeService: Service) {
     return { format, source };
   }
 
+  // Mapping from extensions understood by tsc to the equivalent for node,
+  // as far as getFormat is concerned.
+  const nodeEquivalentExtensions = new Map<string, string>([
+    ['.ts', '.js'],
+    ['.tsx', '.js'],
+    ['.jsx', '.js'],
+    ['.mts', '.mjs'],
+    ['.cts', '.cjs']
+  ]);
+
   async function getFormat(
     url: string,
     context: {},
@@ -227,11 +236,13 @@ export function createEsmHooks(tsNodeService: Service) {
 
     const nativePath = fileURLToPath(url);
 
-    // If file has .ts, .tsx, or .jsx extension, then ask node how it would treat this file if it were .js
+    // If file has extension not understood by node, then ask node how it would treat the emitted extension.
+    // E.g. .mts compiles to .mjs, so ask node how to classify an .mjs file.
     const ext = extname(nativePath);
     let nodeSays: { format: NodeLoaderHooksFormat };
-    if (ext !== '.js' && !tsNodeService.ignored(nativePath)) {
-      nodeSays = await defer(formatUrl(pathToFileURL(nativePath + '.js')));
+    const nodeEquivalentExt = nodeEquivalentExtensions.get(ext);
+    if (nodeEquivalentExt && !tsNodeService.ignored(nativePath)) {
+      nodeSays = await defer(formatUrl(pathToFileURL(nativePath + nodeEquivalentExt)));
     } else {
       nodeSays = await defer();
     }
@@ -283,4 +294,6 @@ export function createEsmHooks(tsNodeService: Service) {
 
     return { source: emittedJs };
   }
+
+  return hooksAPI;
 }
diff --git a/src/index.ts b/src/index.ts
index b3506a4cd..86e254dcd 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -479,6 +479,8 @@ export interface Service {
   installSourceMapSupport(): void;
   /** @internal */
   enableExperimentalEsmLoaderInterop(): void;
+  /** @internal */
+  extensions: Extensions;
 }
 
 /**
@@ -499,14 +501,24 @@ export interface DiagnosticFilter {
 }
 
 /** @internal */
-export function getExtensions(config: _ts.ParsedCommandLine) {
+export type Extensions = ReturnType<typeof getExtensions>;
+
+/** @internal */
+export function getExtensions(config: _ts.ParsedCommandLine, tsVersion: string) {
+  // TS 4.5 is first version to understand .cts, .mts, .cjs, and .mjs extensions
+  const tsSupportsMtsCtsExts = versionGteLt(tsVersion, '4.5.0');
   const tsExtensions = ['.ts'];
   const jsExtensions = [];
 
+  if(tsSupportsMtsCtsExts) tsExtensions.push('.mts', '.cts');
+
   // Enable additional extensions when JSX or `allowJs` is enabled.
   if (config.options.jsx) tsExtensions.push('.tsx');
-  if (config.options.allowJs) jsExtensions.push('.js');
-  if (config.options.jsx && config.options.allowJs) jsExtensions.push('.jsx');
+  if (config.options.allowJs) {
+    jsExtensions.push('.js', '.mjs', '.cjs');
+    if (config.options.jsx) jsExtensions.push('.jsx');
+    if (tsSupportsMtsCtsExts) tsExtensions.push('.mjs', '.cjs');
+  }
   return { tsExtensions, jsExtensions };
 }
 
@@ -529,7 +541,7 @@ export function register(
   }
 
   const originalJsHandler = require.extensions['.js'];
-  const { tsExtensions, jsExtensions } = getExtensions(service.config);
+  const { tsExtensions, jsExtensions } = service.extensions;
   const extensions = [...tsExtensions, ...jsExtensions];
 
   // Expose registered instance globally.
@@ -1296,7 +1308,7 @@ export function create(rawOptions: CreateOptions = {}): Service {
   let active = true;
   const enabled = (enabled?: boolean) =>
     enabled === undefined ? active : (active = !!enabled);
-  const extensions = getExtensions(config);
+  const extensions = getExtensions(config, ts.version);
   const ignored = (fileName: string) => {
     if (!active) return true;
     const ext = extname(fileName);
@@ -1333,6 +1345,7 @@ export function create(rawOptions: CreateOptions = {}): Service {
     addDiagnosticFilter,
     installSourceMapSupport,
     enableExperimentalEsmLoaderInterop,
+    extensions,
   };
 }
 
@@ -1368,14 +1381,29 @@ function registerExtensions(
   service: Service,
   originalJsHandler: (m: NodeModule, filename: string) => any
 ) {
+  const exts = new Set(extensions);
+  // Only way to transform .mts and .cts is via the .js extension.
+  // Can't register those extensions cuz would allow omitting file extension; node requires ext for .cjs and .mjs
+  if(exts.has('.mts') || exts.has('.cts')) exts.add('.js');
+  // Filter extensions which should not be added to `require.extensions`
+  // They may still be handled via the `.js` extension handler.
+  exts.delete('.mts');
+  exts.delete('.cts');
+  exts.delete('.mjs');
+  exts.delete('.cjs');
+
+  // TODO do we care about overriding moduleType for mjs?  No, I don't think so.
+  // Could conditionally register `.mjs` extension when moduleType overrides are configured,
+  // since that is the only situation where we want to avoid node throwing an error.
+
   // Register new extensions.
-  for (const ext of extensions) {
+  for (const ext of exts) {
     registerExtension(ext, service, originalJsHandler);
   }
 
   if (preferTsExts) {
     const preferredExtensions = new Set([
-      ...extensions,
+      ...exts,
       ...Object.keys(require.extensions),
     ]);
 
diff --git a/src/test/index.spec.ts b/src/test/index.spec.ts
index 3b128afdc..b5f8adad4 100644
--- a/src/test/index.spec.ts
+++ b/src/test/index.spec.ts
@@ -183,6 +183,30 @@ test.suite('ts-node', (test) => {
         expect(err).toBe(null);
         expect(stdout).toBe('hello world\n');
       });
+
+      test('should support cts when module = CommonJS', async () => {
+        const { err, stdout } = await exec(
+          [
+            CMD_TS_NODE_WITH_PROJECT_FLAG,
+            '-O "{\\"module\\":"CommonJS"}"',
+            '-pe "import { main } from \'./ts45-ext/ext-cts/index\';main()"',
+          ].join(' ')
+        );
+        expect(err).toBe(null);
+        expect(stdout).toBe('hello world\n');
+      });
+
+      test('should support cts when module = ESNext', async () => {
+        const { err, stdout } = await exec(
+          [
+            CMD_TS_NODE_WITH_PROJECT_FLAG,
+            '-O "{\\"module\\":"ESNext"}"',
+            '-pe "import { main } from \'./ts45-ext/ext-mts/index\';main()"',
+          ].join(' ')
+        );
+        expect(err).toBe(null);
+        expect(stdout).toBe('hello world\n');
+      });
     }
 
     test('should eval code', async () => {
diff --git a/tests/ts45-ext/ext-cts/index.cts b/tests/ts45-ext/ext-cts/index.cts
new file mode 100644
index 000000000..9001625ad
--- /dev/null
+++ b/tests/ts45-ext/ext-cts/index.cts
@@ -0,0 +1,3 @@
+export function main() {
+  return 'hello world';
+}
diff --git a/tests/ts45-ext/ext-cts/tsconfig.json b/tests/ts45-ext/ext-cts/tsconfig.json
new file mode 100644
index 000000000..28900bb1b
--- /dev/null
+++ b/tests/ts45-ext/ext-cts/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "module": "CommonJS"
+  }
+}
diff --git a/tests/ts45-ext/ext-mts/index.mts b/tests/ts45-ext/ext-mts/index.mts
new file mode 100644
index 000000000..9001625ad
--- /dev/null
+++ b/tests/ts45-ext/ext-mts/index.mts
@@ -0,0 +1,3 @@
+export function main() {
+  return 'hello world';
+}
diff --git a/tests/ts45-ext/ext-mts/tsconfig.json b/tests/ts45-ext/ext-mts/tsconfig.json
new file mode 100644
index 000000000..1ac61592b
--- /dev/null
+++ b/tests/ts45-ext/ext-mts/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "module": "ESNext"
+  }
+}