Memory leaks in Node.js happen when your app holds onto memory that it no longer needs. This can lead to increased memory usage over time, eventually causing your app to crash. To fix this, you need to identify where memory isn’t being released. You can use the `node --inspect` flag to enable Chrome DevTools debugging, which provides heap snapshots and memory profiling. The `heapdump` module is another tool that helps you generate memory snapshots. Once you have the snapshot, look for objects that persist in memory longer than they should. Common causes include event listeners not being removed, global variables, or objects stored in closures. By analyzing and fixing these issues, you can prevent memory leaks and ensure stable application performance.