diff --git a/packages/react-dev-utils/globby.js b/packages/react-dev-utils/globby.js
new file mode 100644
index 00000000000..8b32d1d3970
--- /dev/null
+++ b/packages/react-dev-utils/globby.js
@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+var globby = require('globby');
+
+module.exports = globby;
diff --git a/packages/react-dev-utils/package.json b/packages/react-dev-utils/package.json
index 7c3748af901..54d0f286007 100644
--- a/packages/react-dev-utils/package.json
+++ b/packages/react-dev-utils/package.json
@@ -23,6 +23,7 @@
     "getCacheIdentifier.js",
     "getCSSModuleLocalIdent.js",
     "getProcessForPort.js",
+    "globby.js",
     "ignoredFiles.js",
     "immer.js",
     "InlineChunkHtmlPlugin.js",
@@ -53,6 +54,7 @@
     "filesize": "3.6.1",
     "find-up": "3.0.0",
     "global-modules": "1.0.0",
+    "globby": "8.0.1",
     "gzip-size": "5.0.0",
     "immer": "1.7.2",
     "inquirer": "6.2.0",
diff --git a/packages/react-scripts/config/webpack.config.dev.js b/packages/react-scripts/config/webpack.config.dev.js
index 4716345b75c..8a23af48a6e 100644
--- a/packages/react-scripts/config/webpack.config.dev.js
+++ b/packages/react-scripts/config/webpack.config.dev.js
@@ -39,6 +39,9 @@ const publicUrl = '';
 // Get environment variables to inject into our app.
 const env = getClientEnvironment(publicUrl);
 
+// Check if TypeScript is setup
+const useTypeScript = fs.existsSync(paths.appTsConfig);
+
 // style files regexes
 const cssRegex = /\.css$/;
 const cssModuleRegex = /\.module\.css$/;
@@ -150,7 +153,9 @@ module.exports = {
     // https://github.com/facebook/create-react-app/issues/290
     // `web` extension prefixes have been added for better support
     // for React Native Web.
-    extensions: paths.moduleFileExtensions.map(ext => `.${ext}`),
+    extensions: paths.moduleFileExtensions
+      .map(ext => `.${ext}`)
+      .filter(ext => useTypeScript || !ext.includes('ts')),
     alias: {
       // Support React Native Web
       // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
@@ -411,7 +416,7 @@ module.exports = {
       publicPath: publicPath,
     }),
     // TypeScript type checking
-    fs.existsSync(paths.appTsConfig) &&
+    useTypeScript &&
       new ForkTsCheckerWebpackPlugin({
         typescript: resolve.sync('typescript', {
           basedir: paths.appNodeModules,
diff --git a/packages/react-scripts/config/webpack.config.prod.js b/packages/react-scripts/config/webpack.config.prod.js
index bbe9842fd68..654fb3390a2 100644
--- a/packages/react-scripts/config/webpack.config.prod.js
+++ b/packages/react-scripts/config/webpack.config.prod.js
@@ -57,6 +57,9 @@ if (env.stringified['process.env'].NODE_ENV !== '"production"') {
   throw new Error('Production builds must have NODE_ENV=production.');
 }
 
+// Check if TypeScript is setup
+const useTypeScript = fs.existsSync(paths.appTsConfig);
+
 // style files regexes
 const cssRegex = /\.css$/;
 const cssModuleRegex = /\.module\.css$/;
@@ -224,7 +227,9 @@ module.exports = {
     // https://github.com/facebook/create-react-app/issues/290
     // `web` extension prefixes have been added for better support
     // for React Native Web.
-    extensions: paths.moduleFileExtensions.map(ext => `.${ext}`),
+    extensions: paths.moduleFileExtensions
+      .map(ext => `.${ext}`)
+      .filter(ext => useTypeScript || !ext.includes('ts')),
     alias: {
       // Support React Native Web
       // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
diff --git a/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js b/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js
index 50491825da3..b1f1d49c926 100644
--- a/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js
+++ b/packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js
@@ -15,16 +15,33 @@ const path = require('path');
 const paths = require('../../config/paths');
 const os = require('os');
 const immer = require('react-dev-utils/immer').produce;
+const globby = require('react-dev-utils/globby').sync;
 
 function writeJson(fileName, object) {
   fs.writeFileSync(fileName, JSON.stringify(object, null, 2) + os.EOL);
 }
 
+function verifyNoTypeScript() {
+  const typescriptFiles = globby('**/*.(ts|tsx)', { cwd: paths.appSrc });
+  if (typescriptFiles.length > 0) {
+    console.warn(
+      chalk.yellow(
+        `We detected TypeScript in your project (${chalk.bold(
+          `src${path.sep}${typescriptFiles[0]}`
+        )}) and created a ${chalk.bold('tsconfig.json')} file for you.`
+      )
+    );
+    console.warn();
+    return false;
+  }
+  return true;
+}
+
 function verifyTypeScriptSetup() {
   let firstTimeSetup = false;
 
   if (!fs.existsSync(paths.appTsConfig)) {
-    if (!paths.appIndexJs.match(/\.tsx?$/)) {
+    if (verifyNoTypeScript()) {
       return;
     }
     writeJson(paths.appTsConfig, {});
@@ -41,14 +58,12 @@ function verifyTypeScriptSetup() {
     }));
   } catch (_) {
     console.error(
-      chalk.red(
-        'We detected a',
-        chalk.bold('tsconfig.json'),
-        "in your package root but couldn't find an installation of",
-        chalk.bold('typescript') + '.'
+      chalk.bold.red(
+        `It looks like you're trying to use TypeScript but do not have ${chalk.bold(
+          'typescript'
+        )} installed.`
       )
     );
-    console.error();
     console.error(
       chalk.bold(
         'Please install',
@@ -60,9 +75,11 @@ function verifyTypeScriptSetup() {
       )
     );
     console.error(
-      'If you are not trying to use TypeScript, please remove the ' +
-        chalk.cyan('tsconfig.json') +
-        ' file from your package root.'
+      chalk.bold(
+        'If you are not trying to use TypeScript, please remove the ' +
+          chalk.cyan('tsconfig.json') +
+          ' file from your package root (and any TypeScript files).'
+      )
     );
     console.error();
     process.exit(1);
diff --git a/test/fixtures/typescript/package.json b/test/fixtures/typescript/package.json
index 0967ef424bc..c001bab2cd1 100644
--- a/test/fixtures/typescript/package.json
+++ b/test/fixtures/typescript/package.json
@@ -1 +1,5 @@
-{}
+{
+  "dependencies": {
+    "typescript": "3.1.3"
+  }
+}