A protective helmet has an outer shell configured for surrounding a head of a user and at least one accessory attachment rail connected to the outer shell. The accessory attachment rail has a body having a front end, a rear end, and one or more slots between the front end and the rear end. Each of the one or more slots is configured for removably receiving at least one helmet accessory. A locking mechanism is associated with each of the one or more slots for automatically locking the at least one helmet accessory in the one or more slots upon insertion of the at least one helmet accessory within the one or more slots and for preventing removal of the at least one helmet accessory from the one or more slots. At least one connection element is provided for connecting the accessory attachment rail to the outer shell.