Abstract: A lock assembly for a bicycle quick release mechanism comprises: a shaft member having a threaded bore at one end, for connection to the threaded end of the actuating shaft of the quick release mechanism, and spaced from the shaft member one end a transverse bore providing a shoulder facing the actuating shaft; and a housing adapted for connection to the bicycle wheel fork, the housing having a bore for receiving the shaft member and transverse bore therein and the housing having a lock pin adapted for reciprocation to engage the shoulder in one position and a lock adapted to lock the pin in the shoulder engaging position; whereby the wheel cannot be removed from the bicycle, even with the quick release mechanism in a released position, until the lock assembly is unlocked.