A child safety seat includes a seat shell having a seat portion and a backrest, the seat portion having a front end opposite to the backrest, and an extension member connected with the seat shell and having a forward end. The extension member is configurable between a first position where the forward end deploys forward away from the front end of the seat shell, and a second position in which the extension member is retracted toward or removed from the seat shell. The child safety seat has a rear facing configuration of installation, and the forward end of the extension member when in the first position is configured to provide abuttal contact against a seatback of the vehicle seat in the rear facing configuration.