Abstract: A tailgate seat system including: a tailgate rotatable between a raised position and a lowered position; and a backrest assembly mounted to the tailgate. The backrest assembly includes: a support structure mounted to the tailgate; a back panel mounted to the tailgate by way of the support structure; and armrests mounted to the back panel. The backrest assembly is movable between a stowed position and a deployed position. In the stowed position, the support structure is collapsed and both the back panel and the armrests are coplanar and seated on the tailgate. In the deployed position, the support structure is extended to support the back panel and the armrests spaced apart from the tailgate in a non-coplanar relationship.