A nail-driving gun trigger assembly includes a hand-grip, a trigger piece, a safety latch and a release button. The safety latch is mounted on the trigger piece and is movable relative to the trigger piece. The release button is mounted on the trigger piece and is movable relative to the trigger piece. The release button and the safety latch are co-movable with the trigger piece relative to the hand-grip. The trigger piece is stopped from moving by engagement between the safety latch and the hand-grip. The release button is in sliding contact with the safety latch for disengaging the safety latch from the hand-grip and for permitting movement of the trigger piece relative to the hand-grip.