A vehicle seat assembly includes a side support capable of supporting a side portion of the torso of an occupant seated in the seat. The seat has a seatback capable of being tilted up or down relative to a seat cushion. A support shaft extending from a lateral surface part of the seatback in a widthwise direction toward an outside of a vehicle is rotatably supported by a bracket. A spring for urging the seatback in a forward-tilting direction is disposed between the support shaft and the bracket. The bracket and the spring are positioned proximately to a rear surface part of the side support.
