A protective helmet including a shell on which are moveably mounted a shield and a chin guard, the chin guard being moveable between a closed position and an open position and having two lateral branches each provided with a guide in which is meshed a guiding finger fixed on the shell, and the shield being moveable between a lowered position and a lifted position and having two lateral arms articulated on the shell, the helmet having an automatic lifting mechanism of the shield configured to lift the shield from the lowered position during the closing movement of the chin guard and including at least a cam-follower system including: a rotary cam secured to a guiding finger pivotally mounted on the shell and connected in rotation to the corresponding lateral branch of the chin guard by cooperation of form with the guide, and a follower element secured to a lateral arm of the shield, wherein the cam and the follower element are at least in partial contact along a given cam surface.