A helmet assembly having a helmet, a mandible guard, and an accessory attachment system that is used to selectively attach and secure the mandible guard to the helmet is disclosed. In some embodiments, the mandible guard is arranged to be detached from a first side of the helmet while remaining secured to a second side of the helmet. In such embodiments, the mandible guard may be moved outwardly and away from a wearer as the mandible guard pivots around the accessory attachment system attached to the second side of the helmet.