A multi-tiered file locking service provides file locking at the thread and process level, and can optionally include locking at the file system level. A local locking mechanism maintains a list of local locks for threads within a process. When a thread requests a lock for a file, and a local lock is obtained, a process lock for the file may be requested. When no file system locking is used, when the process lock is obtained, the thread receives the lock for the file. When file system locking is used, when the process lock is obtained, a file system lock for the file may be requested. When the file system lock for the file is obtained, the thread receives the lock for the file. The result is a file locking service that functions across threads, processes and nodes in a distributed computing environment.