diff --git a/index.js b/index.js
index 055faee6..a5f0b824 100644
--- a/index.js
+++ b/index.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const fs = require('fs').promises;
+const { existsSync } = require('fs');
 const path = require('path');
 
 const core = require('@actions/core');
@@ -17,6 +18,11 @@ const entry = core.getInput('entry');
     );
   }
 
+  if (!existsSync('node_modules')) {
+    core.warning('node_modules is not present. Running `npm install`...');
+    await exec('npm', ['install']);
+  }
+
   await exec('node', [
     path.join(__dirname, 'node_modules/documentation/bin/documentation.js'),
     'build',