diff --git a/README.md b/README.md
index b7f0709..67bece6 100644
--- a/README.md
+++ b/README.md
@@ -101,6 +101,10 @@ Outputs the name of each file right before it is proccessed. This can be useful
 
 Prevent `git commit` if any files are fixed.
 
+### `--check`
+
+Check that files are correctly formatted, but don't format them. This is useful on CI to verify that all changed files in the current branch were correctly formatted.
+
 <!-- Undocumented = Unsupported :D
 
 ### `--config`
diff --git a/bin/pretty-quick.js b/bin/pretty-quick.js
index 780a4d4..f9fe862 100755
--- a/bin/pretty-quick.js
+++ b/bin/pretty-quick.js
@@ -36,6 +36,12 @@ const prettyQuickResult = prettyQuick(
       console.log(`✍️  Fixing up ${chalk.bold(file)}.`);
     },
 
+    onCheckFile: (file, isFormatted) => {
+      if (!isFormatted) {
+        console.log(`⛔️  Check failed: ${chalk.bold(file)}`);
+      }
+    },
+
     onExamineFile: file => {
       console.log(`🔍  Examining ${chalk.bold(file)}.`);
     },
@@ -56,5 +62,10 @@ if (prettyQuickResult.success) {
       '✗ File had to be prettified and prettyQuick was set to bail mode.'
     );
   }
+  if (prettyQuickResult.errors.indexOf('CHECK_FAILED') !== -1) {
+    console.log(
+      '✗ Code style issues found in the above file(s). Forgot to run Prettier?'
+    );
+  }
   process.exit(1); // ensure git hooks abort
 }
diff --git a/src/formatFiles.js b/src/formatFiles.js
deleted file mode 100644
index 92a8afd..0000000
--- a/src/formatFiles.js
+++ /dev/null
@@ -1,27 +0,0 @@
-import { readFileSync, writeFileSync } from 'fs';
-import { resolveConfig, format } from 'prettier';
-import { join } from 'path';
-
-export default (
-  directory,
-  files,
-  { config, onWriteFile, onExamineFile } = {}
-) => {
-  for (const relative of files) {
-    onExamineFile && onExamineFile(relative);
-    const file = join(directory, relative);
-    const options = resolveConfig.sync(file, { config, editorconfig: true });
-    const input = readFileSync(file, 'utf8');
-    const output = format(
-      input,
-      Object.assign({}, options, {
-        filepath: file,
-      })
-    );
-
-    if (output !== input) {
-      writeFileSync(file, output);
-      onWriteFile && onWriteFile(relative);
-    }
-  }
-};
diff --git a/src/index.js b/src/index.js
index c91c507..e571e8a 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,5 +1,5 @@
 import scms from './scms';
-import formatFiles from './formatFiles';
+import processFiles from './processFiles';
 import createIgnorer from './createIgnorer';
 import createMatcher from './createMatcher';
 import isSupportedExtension from './isSupportedExtension';
@@ -14,12 +14,14 @@ export default (
     restage = true,
     branch,
     bail,
+    check,
     verbose,
     onFoundSinceRevision,
     onFoundChangedFiles,
     onPartiallyStagedFile,
-    onWriteFile,
     onExamineFile,
+    onCheckFile,
+    onWriteFile,
   } = {}
 ) => {
   const scm = scms(currentDirectory);
@@ -60,7 +62,8 @@ export default (
 
   const failReasons = new Set();
 
-  formatFiles(directory, changedFiles, {
+  processFiles(directory, changedFiles, {
+    check,
     config,
     onWriteFile: file => {
       onWriteFile && onWriteFile(file);
@@ -76,6 +79,12 @@ export default (
         }
       }
     },
+    onCheckFile: (file, isFormatted) => {
+      onCheckFile && onCheckFile(file, isFormatted);
+      if (!isFormatted) {
+        failReasons.add('CHECK_FAILED');
+      }
+    },
     onExamineFile: verbose && onExamineFile,
   });
 
diff --git a/src/processFiles.js b/src/processFiles.js
new file mode 100644
index 0000000..77f4cdd
--- /dev/null
+++ b/src/processFiles.js
@@ -0,0 +1,36 @@
+import { readFileSync, writeFileSync } from 'fs';
+import * as prettier from 'prettier';
+import { join } from 'path';
+
+export default (
+  directory,
+  files,
+  { check, config, onExamineFile, onCheckFile, onWriteFile } = {}
+) => {
+  for (const relative of files) {
+    onExamineFile && onExamineFile(relative);
+    const file = join(directory, relative);
+    const options = Object.assign(
+      {},
+      prettier.resolveConfig.sync(file, {
+        config,
+        editorconfig: true,
+      }),
+      { filepath: file }
+    );
+    const input = readFileSync(file, 'utf8');
+
+    if (check) {
+      const isFormatted = prettier.check(input, options);
+      onCheckFile && onCheckFile(relative, isFormatted);
+      continue;
+    }
+
+    const output = prettier.format(input, options);
+
+    if (output !== input) {
+      writeFileSync(file, output);
+      onWriteFile && onWriteFile(relative);
+    }
+  }
+};