A lock assembly includes a fixing plate fixed to an inner side of a door. An inside rose liner is fixed to the fixing plate. A shaft is rotatably mounted in an axial hole of the fixing plate and coupled with a tail piece of an auxiliary lock body. An inside handle includes an inside spindle rotatably mounted in another axial hole of the fixing plate. A control mechanism includes a sliding plate slidably mounted in the inside rose liner, a driving wheel mounted on the inside spindle to turn therewith, and a driven wheel mounted on the shaft to turn therewith. Each of the driving wheel and the driven wheel includes at least one pressing section on an outer periphery thereof for pressing against an associated pressing portion of the sliding plate. The auxiliary lock is simultaneously unlatched when the inside handle is turned.