A man was found with serious head and facial injuries on Smithfield Road at about 2am on Sunday morning after being assaulted.
Initial enquiries suggest that the man was attacked by a group of people who stole several items from him and Whanganui police are appealing for more information.
He was taken to hospital and has since been discharged.
Anyone who may have witnessed the incident or who has relevant information is urged to contact detective Greg Gray at Whanganui police on (06) 215 4138.
Information can also be supplied anonymously via Crimestoppers on 0800 555 111.