A man was mugged in Derby Road, Douglas at around 10pm on Saturday.
Police say he was assaulted and had cash stolen, leaving him shaken, but not seriously injured.
Officers are seeking two men, seen in the area at the time of the incident.
They are described as white and around 30 years old, and one of them was wearing a blue waterproof jacket.
Police say such attacks are rare in the Isle of Man, and they believe there were people in the area who may have seen what happened and could help the investigation.
Anybody with information about the men or the attack is asked to ring Police Headquarters on 631212 or the anonymous Crimestoppers line on 0800 555 111.