A slider window assembly for a vehicle includes a frame portion having an upper rail and a lower rail, with at least one fixed window panel fixed relative to the frame portion and defining an opening. A movable window panel is movable along the upper and lower rails between a closed position and an opened position. A perimeter seal is disposed at the at least one fixed window panel. The perimeter seal includes a single continuous sealing element that circumscribes the opening and that is configured to substantially seal against a surface of the movable window panel about a periphery of the movable window panel when the movable window panel is in its closed position.