The disclosed computer-implemented method for managing delayed allocation on clustered file systems may include (i) receiving, at a global lock manager that stores storage disk allocation information for a plurality of nodes in a clustered file system, a lock request from a node that requests a lock range on a storage disk to store data from a file, (ii) reserving, by the global lock manager, the lock range, (iii) receiving, at the global lock manager, from an additional node, an additional lock request for an additional lock range to store additional data from the file, and (iv) reserving, by the global lock manager, the additional lock range to be adjacent to the lock range on the storage disk based on the additional data on the additional node being from the same file as the data on the node. Various other methods, systems, and computer-readable media are also disclosed.