The invention relates to a fan impeller (5) for a radiator fan module (1) in a motor vehicle as well as to a radiator fan module, the fan impeller comprising: a hub (8), a shroud (9), a plurality of blades (7) that extend from the hub (8) outward and are connected to each other via the shroud (9), and a plurality of streamlining fins (16) which are located between the blades (7), on the bottom side (12) of the shroud (9).