A rear portion structure for a saddle vehicle includes a wide accommodation space for accommodating parts therein while improving the foot grounding property of a rider. A rear fender of a motorcycle has a bottom wall disposed on the inner side of a rear frame in the vehicle widthwise direction, and left and right side walls extending upwardly from the bottom wall. An accommodation space for accommodating a part therein is formed from the bottom wall and the left and right side walls. Left and right first bending portions which individually extend in a longitudinal direction of the vehicle and at which the left and right side walls can individually be bent with respect to the bottom wall are formed between the bottom wall and the left and right side walls. The left and right side walls are inclined inwardly and upwardly along the inner side of the rear frame.