Network user access impersonation for multi-threaded backup applications is described. A backup application receives a first user identity and a second user identity of a set of user identities. The backup application calls a network file system service. The network file system service applies the first user identity to a first thread of a set of threads of a backup application. The network file system service applies the second user identity to a second thread of the set of threads of the backup application. The network file system service enables the first thread to access a first backup file on a first network storage device based on the first user identity. The network file system service enables the second thread to access a second backup file on a second storage device based on the second user identity.