A child safety seat includes a seat body, an armrest, and an actuating mechanism. The seat body includes a seat base. The armrest has a first engaging portion. The actuating mechanism is disposed on the seat body. The actuating mechanism has an actuating portion and a second engaging portion. The actuating portion is exposed from the seat body. The second engaging portion is engaged with the first engaging portion when the armrest is disposed on the seat base. The second engaging portion is disengaged from the first engaging portion when the actuating portion is actuated to move the actuating mechanism, such that the armrest is able to be detached from the seat base.