A slider window assembly for a vehicle includes at least one fixed window panel and a movable window panel. A perimeter seal is disposed at a surface of the fixed window panel and includes a continuous sealing element that circumscribes an opening of the fixed window panel 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 closed. The perimeter seal includes a sealing tab at a corner region of the perimeter seal where an upper sealing portion engages a first elongated side sealing portion. The sealing tab is joined with an elongated sealing lip of the upper sealing portion or the first elongated side sealing portion. The sealing tab extends from the elongated sealing lip toward the surface of the at least one fixed window panel.