A vehicular slider window assembly includes at least one fixed window panel having an opening, and upper and lower rails fixedly disposed at the at least one fixed window panel. A movable window panel is movable along the rails between a closed position and an opened position. A perimeter seal is disposed at a surface of the fixed window panel, with the perimeter seal providing a continuous sealing element that circumscribes the opening and that is configured to seal against a surface of the movable window panel when the movable window panel is closed. The perimeter seal includes elongated sealing portions having respective elongated sealing lips disposed along respective base portions. The perimeter seal is formed via a multi-shot injection molding process, with the base portions formed via a first shot injection molding process and the sealing lips formed along the base portions via a second shot injection molding process.