A lock assembly has a body, a locking cylinder, a latching device, a linking device and a locking mechanism. The locking cylinder has a pushing lug. The linking device is connected to and driven by the latching device. The locking mechanism is driven by the pushing lug of the locking cylinder and has a bolt base, a pushing arm and a locking bolt. The bolt base is mounted slidably in the body and has an edge pushed by the pushing lug on the locking cylinder and a limiting tab. The locking bolt is slidably mounted on the bolt base and abuts with the limiting tab on the bolt base when the locking bolt retracts completely into or extends out from the body. The locking bolt has a blocking tab selectively blocks the linking device.