diff --git a/.pre-commit-hooks.yaml b/.pre-commit-hooks.yaml
index c0d811c..abd0789 100644
--- a/.pre-commit-hooks.yaml
+++ b/.pre-commit-hooks.yaml
@@ -53,6 +53,13 @@
     language: python
     types: [text]
     stages: [commit, push, manual]
+-   id: check_projen_files
+    name: check projen files
+    description: checks if projen files were not updated manually.
+    entry: check_projen_files
+    language: python
+    types: [text]
+    stages: [push, manual]
 -   id: pretty-format-json
     name: pretty format json
     description: sets a standard for formatting json files.
diff --git a/README.md b/README.md
index 9ae7ec5..b6030b8 100644
--- a/README.md
+++ b/README.md
@@ -64,6 +64,9 @@ Checks that scripts with shebangs are executable.
 #### `check-symlinks`
 Checks for symlinks which do not point to anything.
 
+#### `check-projen-files`
+Checks for projen files that were updated manually.
+
 #### `check-toml`
 Attempts to load all TOML files to verify syntax.
 
diff --git a/pre_commit_hooks/check_projen_files.py b/pre_commit_hooks/check_projen_files.py
new file mode 100644
index 0000000..3aa2d8a
--- /dev/null
+++ b/pre_commit_hooks/check_projen_files.py
@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+import subprocess
+import sys
+
+def main():
+    projen_process = subprocess.run('yarn projen', shell=True)
+    
+    if projen_process.returncode != 0:
+        print(f'Error: "yarn projen" failed with exit status {projen_process.returncode}')
+        sys.exit(projen_process.returncode)
+
+    git_status = subprocess.run('git diff', capture_output=True, shell=True, text=True)
+    if git_status.stdout.strip():
+        print("Uncommitted changes found:")
+        print(git_status.stdout)
+        print('Have you forgotten to run "yarn projen" and commit changes?')
+        sys.exit(1)
+
+if __name__ == '__main__':
+    raise SystemExit(main())
\ No newline at end of file