A transmission mechanism of a lock assembly includes a base; a core assembly partially received in the base and having therein a core adapted to connect to the rod so as to control movement of the rod; an operating element rotatably connected to the base; a clutch device movably received in the base and selectively engaged with the operating element; a driving device received in the core assembly to drive the clutch device to move toward/away from the operating element; and an activation device connected to the base to control operation of the driving device such that the latch is moved with assistance of the rotation of the operating element when the clutch device is connected to the operating element and the latch is immovable when the clutch device is away from engagement with the operating element.
