diff --git a/plugin.jest.js b/plugin.jest.js
index 683e502..e9748aa 100644
--- a/plugin.jest.js
+++ b/plugin.jest.js
@@ -543,6 +543,102 @@ describe('CspHtmlWebpackPlugin', () => {
     });
   });
 
+  describe('Adding integrity attribute', () => {
+    it('adds an integrity attribute to linked scripts and styles', (done) => {
+      const config = createWebpackConfig(
+        [
+          new HtmlWebpackPlugin({
+            filename: path.join(WEBPACK_OUTPUT_DIR, 'index.html'),
+            template: path.join(
+              __dirname,
+              'test-utils',
+              'fixtures',
+              'external-scripts-styles.html'
+            ),
+          }),
+          new MiniCssExtractPlugin(),
+          new CspHtmlWebpackPlugin(),
+        ],
+        undefined,
+        'index-styled.js',
+        {
+          module: {
+            rules: [
+              {
+                test: /\.css$/,
+                use: [MiniCssExtractPlugin.loader, 'css-loader'],
+              },
+            ],
+          },
+        }
+      );
+
+      webpackCompile(config, (_, html) => {
+        const scripts = html['index.html']('script[src]');
+        const styles = html['index.html']('link[rel="stylesheet"]');
+
+        scripts.each((i, script) => {
+          if (!script.attribs.src.startsWith('http')) {
+            expect(script.attribs.integrity).toEqual("sha256-IDmpTcnLo5Niek0rbHm9EEQtYiqYHApvDU+Rta9RdVU=");
+          } else {
+            expect(script.attribs.integrity).toBeUndefined();
+          }
+        })
+        styles.each((i, style) => {
+          if (!style.attribs.href.startsWith('http')) {
+            expect(style.attribs.integrity).toEqual("sha256-bFK7QzTObijstzDDaq2yN82QIYcoYx/EDD87NWCGiPw=");
+          } else {
+            expect(style.attribs.integrity).toBeUndefined();
+          }
+        });
+        done();
+      });
+    });
+
+    it('does not add an integrity attribute to inline scripts or styles', (done) => {
+      const config = createWebpackConfig(
+        [
+          new HtmlWebpackPlugin({
+            filename: path.join(WEBPACK_OUTPUT_DIR, 'index.html'),
+            template: path.join(
+              __dirname,
+              'test-utils',
+              'fixtures',
+              'with-script-and-style.html'
+            ),
+          }),
+          new MiniCssExtractPlugin(),
+          new CspHtmlWebpackPlugin(),
+        ],
+        undefined,
+        'index-styled.js',
+        {
+          module: {
+            rules: [
+              {
+                test: /\.css$/,
+                use: [MiniCssExtractPlugin.loader, 'css-loader'],
+              },
+            ],
+          },
+        }
+      );
+
+      webpackCompile(config, (_, html) => {
+        const scripts = html['index.html']('script:not([src])');
+        const styles = html['index.html']('style');
+
+        scripts.each((i, script) => {
+          expect(script.attribs.integrity).toBeUndefined();
+        })
+        styles.each((i, style) => {
+          expect(style.attribs.integrity).toBeUndefined();
+        });
+        done();
+      });
+    });
+  });
+
   describe('Hash / Nonce enabled check', () => {
     it("doesn't add hashes to any policy rule if that policy rule has been globally disabled", (done) => {
       const config = createWebpackConfig([
diff --git a/plugin.js b/plugin.js
index fd8aa21..68359d9 100644
--- a/plugin.js
+++ b/plugin.js
@@ -81,6 +81,9 @@ class CspHtmlWebpackPlugin {
     // the additional options that this plugin allows
     this.opts = Object.freeze({ ...defaultAdditionalOpts, ...additionalOpts });
 
+    // the calculated hashes for each file, indexed by filename
+    this.hashes = {};
+
     // valid hashes from https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src#Sources
     if (!['sha256', 'sha384', 'sha512'].includes(this.opts.hashingMethod)) {
       throw new Error(
@@ -262,6 +265,19 @@ class CspHtmlWebpackPlugin {
     return `'${this.opts.hashingMethod}-${hashed}'`;
   }
 
+  /**
+   * Gets the hash of a file that is a webpack asset, storing the hash in a cache.
+   * @param assets
+   * @param {string} filename
+   * @returns {string}
+   */
+  hashFile(assets, filename) {
+    if (!Object.prototype.hasOwnProperty.call(this.hashes, filename)) {
+      this.hashes[filename] = this.hash(assets[filename].source());
+    }
+    return this.hashes[filename];
+  }
+
   /**
    * Calculates shas of the policy / selector we define
    * @param {object} $ - the Cheerio instance
@@ -345,12 +361,12 @@ class CspHtmlWebpackPlugin {
       .filter((filename) =>
         includedScripts.includes(path.join(this.publicPath, filename))
       )
-      .map((filename) => this.hash(compilation.assets[filename].source()));
+      .map((filename) => this.hashFile(compilation.assets, filename));
     const linkedStyleShas = this.styleFilesToHash
       .filter((filename) =>
         includedStyles.includes(path.join(this.publicPath, filename))
       )
-      .map((filename) => this.hash(compilation.assets[filename].source()));
+      .map((filename) => this.hashFile(compilation.assets, filename));
 
     const builtPolicy = this.buildPolicy({
       ...this.policy,
@@ -395,6 +411,45 @@ class CspHtmlWebpackPlugin {
     return compileCb(null, htmlPluginData);
   }
 
+  /**
+   * Remove the public path from a URL, if present
+   * @param publicPath
+   * @param {string} path
+   * @returns {string}
+   */
+  getFilename(publicPath, path) {
+    if (!publicPath || !path.startsWith(publicPath)) {
+      return path;
+    }
+    return path.substr(publicPath.length);
+  }
+
+  /**
+   * Add integrity attributes to asset tags
+   * @param compilation
+   * @param htmlPluginData
+   * @param compileCb
+   */
+  addIntegrityAttributes(compilation, htmlPluginData, compileCb) {
+    if (this.hashEnabled['script-src'] !== false) {
+      htmlPluginData.assetTags.scripts.filter(tag => tag.attributes.src).forEach(tag => {
+        const filename = this.getFilename(compilation.options.output.publicPath, tag.attributes.src);
+        if (filename in compilation.assets) {
+          tag.attributes.integrity = this.hashFile(compilation.assets, filename).slice(1, -1);
+        }
+      });
+    }
+    if (this.hashEnabled['style-src'] !== false) {
+      htmlPluginData.assetTags.styles.filter(tag => tag.attributes.href).forEach(tag => {
+        const filename = this.getFilename(compilation.options.output.publicPath, tag.attributes.href);
+        if (filename in compilation.assets) {
+          tag.attributes.integrity = this.hashFile(compilation.assets, filename).slice(1, -1);
+        }
+      });
+    }
+    return compileCb(null, htmlPluginData);
+  }
+
   /**
    * Hooks into webpack to collect assets and hash them, build the policy, and add it into our HTML template
    * @param compiler
@@ -413,6 +468,10 @@ class CspHtmlWebpackPlugin {
         'CspHtmlWebpackPlugin',
         this.getFilesToHash.bind(this)
       );
+      HtmlWebpackPlugin.getHooks(compilation).alterAssetTags.tapAsync(
+        'CspHtmlWebpackPlugin',
+        this.addIntegrityAttributes.bind(this, compilation)
+      )
     });
   }
 }