Abstract: A seat assembly for a motor vehicle includes a seat with a seat cushion part, and a seat slide device. The seat slide device includes a pair of stationary rails and a pair of movable rails which mount thereon the seat cushion part and slidably engages with the stationary rails. A cover member is connected to a rear portion of the seat cushion part and covers a rear end portion of the seat slide device. The cover member has a pair of recesses through which the stationary rails pass when the seat cushion part moves forward to a certain position relative to the stationary rails. A lid member is pivotally connected to the cover member in a manner to close the recess.