diff --git a/packages/react-scripts/config/webpack.config.dev.js b/packages/react-scripts/config/webpack.config.dev.js
index aea37eab6bc..3cb87711f51 100644
--- a/packages/react-scripts/config/webpack.config.dev.js
+++ b/packages/react-scripts/config/webpack.config.dev.js
@@ -16,6 +16,7 @@ const HtmlWebpackPlugin = require('html-webpack-plugin');
 const CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
 const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
 const WatchMissingNodeModulesPlugin = require('react-dev-utils/WatchMissingNodeModulesPlugin');
+const DuplicatePackageCheckerPlugin = require('duplicate-package-checker-webpack-plugin');
 const getClientEnvironment = require('./env');
 const paths = require('./paths');
 
@@ -236,6 +237,9 @@ 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 about duplicate dependencies.
+    // See https://github.com/facebookincubator/create-react-app/issues/1844
+    new DuplicatePackageCheckerPlugin(),
     // 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/packages/react-scripts/config/webpack.config.prod.js b/packages/react-scripts/config/webpack.config.prod.js
index 218eb46bb0c..6fca17e8c1f 100644
--- a/packages/react-scripts/config/webpack.config.prod.js
+++ b/packages/react-scripts/config/webpack.config.prod.js
@@ -16,6 +16,7 @@ const HtmlWebpackPlugin = require('html-webpack-plugin');
 const ExtractTextPlugin = require('extract-text-webpack-plugin');
 const ManifestPlugin = require('webpack-manifest-plugin');
 const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
+const DuplicatePackageCheckerPlugin = require('duplicate-package-checker-webpack-plugin');
 const paths = require('./paths');
 const getClientEnvironment = require('./env');
 
@@ -274,6 +275,9 @@ module.exports = {
     new ExtractTextPlugin({
       filename: cssFilename,
     }),
+    // Warn about duplicate dependencies.
+    // See https://github.com/facebookincubator/create-react-app/issues/1844
+    new DuplicatePackageCheckerPlugin(),
     // Generate a manifest file which contains a mapping of all asset filenames
     // to their corresponding output file so that tools can pick it up without
     // having to parse `index.html`.
diff --git a/packages/react-scripts/package.json b/packages/react-scripts/package.json
index b2cb03bb972..84bc9ed3df8 100644
--- a/packages/react-scripts/package.json
+++ b/packages/react-scripts/package.json
@@ -35,6 +35,7 @@
     "css-loader": "0.26.2",
     "detect-port": "1.1.0",
     "dotenv": "2.0.0",
+    "duplicate-package-checker-webpack-plugin": "^1.2.3",
     "eslint": "3.16.1",
     "eslint-config-react-app": "^0.6.1",
     "eslint-loader": "1.6.3",