diff --git a/lib/internal/modules/esm/translators.js b/lib/internal/modules/esm/translators.js
index 87f271adcd3e50..c2ca465c905103 100644
--- a/lib/internal/modules/esm/translators.js
+++ b/lib/internal/modules/esm/translators.js
@@ -129,8 +129,20 @@ const { requestTypes: { kRequireInImportedCJS } } = require('internal/modules/es
  * @param {boolean} isMain - Whether the module is the entrypoint
  */
 function loadCJSModule(module, source, url, filename, isMain) {
-  const compileResult = compileFunctionForCJSLoader(source, filename, false /* is_sea_main */, false);
+  // Validate source before compilation to prevent internal assertion errors.
+  // Without this check, null or undefined source causes ERR_INTERNAL_ASSERTION
+  // when passed to compileFunctionForCJSLoader.
+  // Refs: https://github.com/nodejs/node/issues/60401
+  if (source === null || source === undefined || source === '') {
+    throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
+      'non-empty string',
+      'load',
+      'source',
+      source,
+    );
+  }
 
+  const compileResult = compileFunctionForCJSLoader(source, filename, false /* is_sea_main */, false);
   const { function: compiledWrapper, sourceMapURL, sourceURL } = compileResult;
   // Cache the source map for the cjs module if present.
   if (sourceMapURL) {
diff --git a/test/parallel/test-esm-loader-null-source.js b/test/parallel/test-esm-loader-null-source.js
new file mode 100644
index 00000000000000..3e57eae08a4a91
--- /dev/null
+++ b/test/parallel/test-esm-loader-null-source.js
@@ -0,0 +1,131 @@
+'use strict';
+
+// Test that ESM loader handles null/undefined source gracefully
+// and throws meaningful error instead of ERR_INTERNAL_ASSERTION.
+// Refs: https://github.com/nodejs/node/issues/60401
+
+const common = require('../common');
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+const fixtures = require('../common/fixtures');
+
+// Reusable loader functions
+function createNullLoader() {
+  return function load(url, context, next) {
+    if (url.includes('test-null-source')) {
+      return { format: 'commonjs', source: null, shortCircuit: true };
+    }
+    return next(url);
+  };
+}
+
+function createUndefinedLoader() {
+  return function load(url, context, next) {
+    if (url.includes('test-undefined-source')) {
+      return { format: 'commonjs', source: undefined, shortCircuit: true };
+    }
+    return next(url);
+  };
+}
+
+function createEmptyLoader() {
+  return function load(url, context, next) {
+    if (url.includes('test-empty-source')) {
+      return { format: 'commonjs', source: '', shortCircuit: true };
+    }
+    return next(url);
+  };
+}
+
+// Helper to run test with custom loader
+function runTestWithLoader(loaderFn, testUrl) {
+  const loaderCode = `export ${loaderFn.toString()}`;
+  
+  const result = spawnSync(
+    process.execPath,
+    [
+      '--no-warnings',
+      '--input-type=module',
+      '--eval',
+      `
+      import { register } from 'node:module';
+      import assert from 'node:assert';
+      
+      register('data:text/javascript,' + encodeURIComponent(${JSON.stringify(loaderCode)}));
+      
+      await assert.rejects(
+        import(${JSON.stringify(testUrl)}),
+        { code: 'ERR_INVALID_RETURN_PROPERTY_VALUE' }
+      );
+      `,
+    ],
+    { encoding: 'utf8' }
+  );
+
+  return result;
+}
+
+// Test case 1: Loader returning null source
+{
+  const result = runTestWithLoader(
+    createNullLoader(),
+    'file:///test-null-source.js'
+  );
+
+  const output = result.stdout + result.stderr;
+  
+  assert.ok(
+    !output.includes('ERR_INTERNAL_ASSERTION'),
+    'Should not throw ERR_INTERNAL_ASSERTION. Output: ' + output
+  );
+
+  assert.strictEqual(
+    result.status,
+    0,
+    'Process should exit with code 0. Output: ' + output
+  );
+}
+
+// Test case 2: Loader returning undefined source
+{
+  const result = runTestWithLoader(
+    createUndefinedLoader(),
+    'file:///test-undefined-source.js'
+  );
+
+  const output = result.stdout + result.stderr;
+  
+  assert.ok(
+    !output.includes('ERR_INTERNAL_ASSERTION'),
+    'Should not throw ERR_INTERNAL_ASSERTION. Output: ' + output
+  );
+
+  assert.strictEqual(
+    result.status,
+    0,
+    'Process should exit with code 0. Output: ' + output
+  );
+}
+
+// Test case 3: Loader returning empty string source
+{
+  const fixtureURL = fixtures.fileURL('es-modules/loose.js');
+  
+  const result = runTestWithLoader(
+    createEmptyLoader(),
+    fixtureURL.href
+  );
+
+  const output = result.stdout + result.stderr;
+  
+  assert.ok(
+    !output.includes('ERR_INTERNAL_ASSERTION'),
+    'Should not throw ERR_INTERNAL_ASSERTION. Output: ' + output
+  );
+
+  assert.strictEqual(
+    result.status,
+    0,
+    'Process should exit with code 0. Output: ' + output
+  );
+}