Police are searching for a man who grabbed a woman's buttocks in Nedlands yesterday.

About 11.20am a 24-year-old University of WA student was walking down Bruce Street in Nedlands when she noticed a male walk up from Edward Street and then turn into Bruce Street behind her.

Police have released this composite image of the man who grabbed a woman's buttocks in Nedlands on May 28.

The man came up behind her and whispered in her ear, and as she turned around, exposed his penis.

He then grabbed hold of her buttocks, before she screamed and ran away.