diff --git a/packages/babel-helper-fixtures/src/index.ts b/packages/babel-helper-fixtures/src/index.ts
index 7463cf0bdcc2..6baa9dc348c6 100644
--- a/packages/babel-helper-fixtures/src/index.ts
+++ b/packages/babel-helper-fixtures/src/index.ts
@@ -64,7 +64,7 @@ function shouldIgnore(name, ignore?: Array<string>) {
   );
 }
 
-const EXTENSIONS = [".js", ".mjs", ".ts", ".tsx"];
+const EXTENSIONS = [".js", ".mjs", ".ts", ".tsx", ".cts", ".mts"];
 
 function findFile(filepath: string, allowJSON?: boolean) {
   const matches = [];
@@ -134,6 +134,7 @@ function pushTask(taskName, taskDir, suite, suiteName) {
         ? taskOpts.BABEL_8_BREAKING === false
         : taskOpts.BABEL_8_BREAKING === true),
     options: taskOpts,
+    doNotSetSourceType: taskOpts.DO_NOT_SET_SOURCE_TYPE,
     externalHelpers:
       taskOpts.externalHelpers ??
       !!tryResolve("@babel/plugin-external-helpers"),
@@ -162,6 +163,7 @@ function pushTask(taskName, taskDir, suite, suiteName) {
   };
 
   delete taskOpts.BABEL_8_BREAKING;
+  delete taskOpts.DO_NOT_SET_SOURCE_TYPE;
 
   // If there's node requirement, check it before pushing task
   if (taskOpts.minNodeVersion) {
diff --git a/packages/babel-helper-transform-fixture-test-runner/src/index.ts b/packages/babel-helper-transform-fixture-test-runner/src/index.ts
index cfbe4fd9283c..33c2c235994b 100644
--- a/packages/babel-helper-transform-fixture-test-runner/src/index.ts
+++ b/packages/babel-helper-transform-fixture-test-runner/src/index.ts
@@ -230,6 +230,7 @@ function run(task) {
     expect: expected,
     exec,
     options: opts,
+    doNotSetSourceType,
     optionsDir,
     validateLogs,
     ignoreOutput,
@@ -245,7 +246,7 @@ function run(task) {
       filename: self.loc,
       filenameRelative: self.filename,
       sourceFileName: self.filename,
-      sourceType: "script",
+      ...(doNotSetSourceType ? {} : { sourceType: "script" }),
       babelrc: false,
       configFile: false,
       inputSourceMap: task.inputSourceMap || undefined,
diff --git a/packages/babel-preset-typescript/src/index.js b/packages/babel-preset-typescript/src/index.js
index e384e41c2424..52c71526d63a 100644
--- a/packages/babel-preset-typescript/src/index.js
+++ b/packages/babel-preset-typescript/src/index.js
@@ -8,6 +8,7 @@ export default declare((api, opts) => {
   const {
     allExtensions,
     allowNamespaces,
+    disallowJSXAmbiguity,
     isTSX,
     jsxPragma,
     jsxPragmaFrag,
@@ -16,17 +17,19 @@ export default declare((api, opts) => {
   } = normalizeOptions(opts);
 
   const pluginOptions = process.env.BABEL_8_BREAKING
-    ? isTSX => ({
+    ? (isTSX, disallowJSXAmbiguity) => ({
         allowNamespaces,
+        disallowJSXAmbiguity,
         isTSX,
         jsxPragma,
         jsxPragmaFrag,
         onlyRemoveTypeImports,
         optimizeConstEnums,
       })
-    : isTSX => ({
+    : (isTSX, disallowJSXAmbiguity) => ({
         allowDeclareFields: opts.allowDeclareFields,
         allowNamespaces,
+        disallowJSXAmbiguity,
         isTSX,
         jsxPragma,
         jsxPragmaFrag,
@@ -38,21 +41,33 @@ export default declare((api, opts) => {
     overrides: allExtensions
       ? [
           {
-            plugins: [[transformTypeScript, pluginOptions(isTSX)]],
+            plugins: [
+              [transformTypeScript, pluginOptions(isTSX, disallowJSXAmbiguity)],
+            ],
           },
         ]
-      : [
+      : // Only set 'test' if explicitly requested, since it requires that
+        // Babel is being called`
+        [
           {
-            // Only set 'test' if explicitly requested, since it requires that
-            // Babel is being called`
             test: /\.ts$/,
-            plugins: [[transformTypeScript, pluginOptions(false)]],
+            plugins: [[transformTypeScript, pluginOptions(false, false)]],
+          },
+          {
+            test: /\.mts$/,
+            sourceType: "module",
+            plugins: [[transformTypeScript, pluginOptions(false, true)]],
+          },
+          {
+            test: /\.cts$/,
+            sourceType: "script",
+            plugins: [[transformTypeScript, pluginOptions(false, true)]],
           },
           {
-            // Only set 'test' if explicitly requested, since it requires that
-            // Babel is being called`
             test: /\.tsx$/,
-            plugins: [[transformTypeScript, pluginOptions(true)]],
+            // disallowJSXAmbiguity is a no-op when parsing TSX, since it's
+            // always disallowed.
+            plugins: [[transformTypeScript, pluginOptions(true, false)]],
           },
         ],
   };
diff --git a/packages/babel-preset-typescript/src/normalize-options.js b/packages/babel-preset-typescript/src/normalize-options.js
index 6812fac324b1..f8ac91880ac5 100644
--- a/packages/babel-preset-typescript/src/normalize-options.js
+++ b/packages/babel-preset-typescript/src/normalize-options.js
@@ -7,6 +7,7 @@ export default function normalizeOptions(options = {}) {
   const TopLevelOptions = {
     allExtensions: "allExtensions",
     allowNamespaces: "allowNamespaces",
+    disallowJSXAmbiguity: "disallowJSXAmbiguity",
     isTSX: "isTSX",
     jsxPragma: "jsxPragma",
     jsxPragmaFrag: "jsxPragmaFrag",
@@ -54,6 +55,18 @@ export default function normalizeOptions(options = {}) {
     v.invariant(allExtensions, "isTSX:true requires allExtensions:true");
   }
 
+  const disallowJSXAmbiguity = v.validateBooleanOption(
+    TopLevelOptions.disallowJSXAmbiguity,
+    options.disallowJSXAmbiguity,
+    false,
+  );
+  if (disallowJSXAmbiguity) {
+    v.invariant(
+      allExtensions,
+      "disallowJSXAmbiguity:true requires allExtensions:true",
+    );
+  }
+
   const optimizeConstEnums = v.validateBooleanOption(
     TopLevelOptions.optimizeConstEnums,
     options.optimizeConstEnums,
@@ -63,6 +76,7 @@ export default function normalizeOptions(options = {}) {
   return {
     allExtensions,
     allowNamespaces,
+    disallowJSXAmbiguity,
     isTSX,
     jsxPragma,
     jsxPragmaFrag,
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-cts/input.cts b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-cts/input.cts
new file mode 100644
index 000000000000..856f26b34c30
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-cts/input.cts
@@ -0,0 +1 @@
+import "x";
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-cts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-cts/options.json
new file mode 100644
index 000000000000..afbed324e92a
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-cts/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'import' and 'export' may appear only with 'sourceType: \"module\"' (1:0)"
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-mts/input.mts b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-mts/input.mts
new file mode 100644
index 000000000000..856f26b34c30
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-mts/input.mts
@@ -0,0 +1 @@
+import "x";
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-mts/output.mjs b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-mts/output.mjs
new file mode 100644
index 000000000000..856f26b34c30
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/import-in-mts/output.mjs
@@ -0,0 +1 @@
+import "x";
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/options.json
new file mode 100644
index 000000000000..d1e62be8eb76
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/options.json
@@ -0,0 +1,4 @@
+{
+  "DO_NOT_SET_SOURCE_TYPE": true,
+  "presets": ["typescript"]
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-cts/input.cts b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-cts/input.cts
new file mode 100644
index 000000000000..35a8b2e1277f
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-cts/input.cts
@@ -0,0 +1 @@
+<T> x;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-cts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-cts/options.json
new file mode 100644
index 000000000000..d59f14ff0b1b
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-cts/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "This syntax is reserved in files with the .mts or .cts extension. Use an `as` expression instead. (1:0)"
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-mts/input.mts b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-mts/input.mts
new file mode 100644
index 000000000000..35a8b2e1277f
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-mts/input.mts
@@ -0,0 +1 @@
+<T> x;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-mts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-mts/options.json
new file mode 100644
index 000000000000..d59f14ff0b1b
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-mts/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "This syntax is reserved in files with the .mts or .cts extension. Use an `as` expression instead. (1:0)"
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/input.ts b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/input.ts
new file mode 100644
index 000000000000..35a8b2e1277f
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/input.ts
@@ -0,0 +1 @@
+<T> x;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/options.json
new file mode 100644
index 000000000000..55a498f5e8b2
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/options.json
@@ -0,0 +1,3 @@
+{
+  "DO_NOT_SET_SOURCE_TYPE": false
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/output.js b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/output.js
new file mode 100644
index 000000000000..6c650fc54be1
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-assertion-in-ts/output.js
@@ -0,0 +1 @@
+x;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-cts/input.mts b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-cts/input.mts
new file mode 100644
index 000000000000..c6c773b424dd
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-cts/input.mts
@@ -0,0 +1 @@
+<T>() => 0;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-cts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-cts/options.json
new file mode 100644
index 000000000000..656905ed2daf
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-cts/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "This syntax is reserved in files with the .mts or .cts extension. Add a trailing comma, as in `<T,>() => ...`. (1:0)"
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-mts/input.mts b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-mts/input.mts
new file mode 100644
index 000000000000..c6c773b424dd
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-mts/input.mts
@@ -0,0 +1 @@
+<T>() => 0;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-mts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-mts/options.json
new file mode 100644
index 000000000000..656905ed2daf
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-mts/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "This syntax is reserved in files with the .mts or .cts extension. Add a trailing comma, as in `<T,>() => ...`. (1:0)"
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/input.ts b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/input.ts
new file mode 100644
index 000000000000..c6c773b424dd
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/input.ts
@@ -0,0 +1 @@
+<T>() => 0;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/options.json
new file mode 100644
index 000000000000..55a498f5e8b2
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/options.json
@@ -0,0 +1,3 @@
+{
+  "DO_NOT_SET_SOURCE_TYPE": false
+}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/output.js b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/output.js
new file mode 100644
index 000000000000..d4bf221471c1
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/type-param-arrow-in-ts/output.js
@@ -0,0 +1 @@
+() => 0;
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-cts/input.cts b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-cts/input.cts
new file mode 100644
index 000000000000..66e645012e48
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-cts/input.cts
@@ -0,0 +1 @@
+with (x) {}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-cts/output.js b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-cts/output.js
new file mode 100644
index 000000000000..66e645012e48
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-cts/output.js
@@ -0,0 +1 @@
+with (x) {}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-mts/input.mts b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-mts/input.mts
new file mode 100644
index 000000000000..66e645012e48
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-mts/input.mts
@@ -0,0 +1 @@
+with (x) {}
diff --git a/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-mts/options.json b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-mts/options.json
new file mode 100644
index 000000000000..25577a776804
--- /dev/null
+++ b/packages/babel-preset-typescript/test/fixtures/node-extensions/with-in-mts/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'with' in strict mode. (1:0)"
+}
diff --git a/packages/babel-preset-typescript/test/normalize-options.spec.js b/packages/babel-preset-typescript/test/normalize-options.spec.js
index d0a10d18087b..de9341aca9e8 100644
--- a/packages/babel-preset-typescript/test/normalize-options.spec.js
+++ b/packages/babel-preset-typescript/test/normalize-options.spec.js
@@ -78,16 +78,17 @@ describe("normalize options", () => {
     );
     it("default values", () => {
       expect(normalizeOptions({})).toMatchInlineSnapshot(`
-        Object {
-          "allExtensions": false,
-          "allowNamespaces": true,
-          "isTSX": false,
-          "jsxPragma": undefined,
-          "jsxPragmaFrag": "React.Fragment",
-          "onlyRemoveTypeImports": undefined,
-          "optimizeConstEnums": false,
-        }
-      `);
+Object {
+  "allExtensions": false,
+  "allowNamespaces": true,
+  "disallowJSXAmbiguity": false,
+  "isTSX": false,
+  "jsxPragma": undefined,
+  "jsxPragmaFrag": "React.Fragment",
+  "onlyRemoveTypeImports": undefined,
+  "optimizeConstEnums": false,
+}
+`);
     });
   });
 });