To provide a rear portion structure of a saddle-type vehicle, which enables securement of a space for arranging vehicle-mounted components on the upper side of a drive chain at a position apart from a pivot shaft. A motorcycle includes a rear wheel swingably provided on a main member via a swing arm, a drive chain entrained about a driven sprocket provided on the rear wheel and a drive sprocket, and a seat frame. An air-exhaust pipe extends from an engine on a lower portion of the seat frame, an extending portion extends rearward of the vehicle from the seat frame, and a chain guide roller is mounted on the extending portion.