diff --git a/config/webpack.config.dev.js b/config/webpack.config.dev.js
index a3db11f8ec7..e53be7aabb2 100644
--- a/config/webpack.config.dev.js
+++ b/config/webpack.config.dev.js
@@ -12,6 +12,7 @@ var autoprefixer = require('autoprefixer');
 var webpack = require('webpack');
 var HtmlWebpackPlugin = require('html-webpack-plugin');
 var CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
+var CheckFilenamePlugin = require('check-filename-webpack-plugin');
 var WatchMissingNodeModulesPlugin = require('../scripts/utils/WatchMissingNodeModulesPlugin');
 var paths = require('./paths');
 var env = require('./env');
@@ -66,7 +67,8 @@ module.exports = {
   },
   resolve: {
     // These are the reasonable defaults supported by the Node ecosystem.
-    extensions: ['.js', '.json', ''],
+    // We also include .jsx extension in order to warn with CheckFilenamePlugin.
+    extensions: ['.jsx', '.js', '.json', ''],
     alias: {
       // This `alias` section can be safely removed after ejection.
       // We do this because `babel-runtime` may be inside `react-scripts`,
@@ -179,6 +181,14 @@ module.exports = {
     // a plugin that prints an error when you attempt to do this.
     // See https://github.com/facebookincubator/create-react-app/issues/240
     new CaseSensitivePathsPlugin(),
+    // Warn on using .jsx files, prefer using .js only.
+    // See https://github.com/facebookincubator/create-react-app/issues/290
+    new CheckFilenamePlugin({
+      regex: /\.jsx$/,
+      error: function(filename) {
+        return 'Module load aborted: .jsx extensions are not allowed, use .js extensions only. See create-react-app/issues/290 for more info.\n\tFor: ' + filename;
+      }
+    }),
     // If you require a missing module and then `npm install` it, you still have
     // to restart the development server for Webpack to discover it. This plugin
     // makes the discovery automatic so you don't have to restart.
diff --git a/package.json b/package.json
index bf3d853af2a..279e76e808c 100644
--- a/package.json
+++ b/package.json
@@ -46,6 +46,7 @@
     "babel-runtime": "6.11.6",
     "case-sensitive-paths-webpack-plugin": "1.1.2",
     "chalk": "1.1.3",
+    "check-filename-webpack-plugin": "^1.0.0",
     "connect-history-api-fallback": "1.2.0",
     "cross-spawn": "4.0.0",
     "css-loader": "0.23.1",
diff --git a/template/README.md b/template/README.md
index 441953eef69..d4f129e1381 100644
--- a/template/README.md
+++ b/template/README.md
@@ -81,6 +81,8 @@ You need to **put any JS and CSS files inside `src`**, or Webpack won’t see th
 You can, however, create more top-level directories.  
 They will not be included in the production build so you can use them for things like documentation.
 
+> NOTE: Only use `.js` file extensions for all JavaScript files inside `src`, including any React components. `.jsx` is explicitly not allowed, and an error will be thrown during compilation. See [create-react-app/issues/290](https://github.com/facebookincubator/create-react-app/issues/290) for more info.
+
 ## Available Scripts
 
 In the project directory, you can run: