Thieves punched a security guard and stole his car outside Hemmings Park in Dandenong.
He was sitting in the vehicle about 1.45am on Friday 3 March and noted 15 youths in the Princes Highway park.
Greater Dandenong CIU Detective Senior Constable Renae Du Plessis said five of them approached the victim and punched him in the face through his open window.
He got out of the car and the thieves took his keys and drove away.
The 30-year-old Oakleigh East man suffered bruising to his face in the attack.
Call Crime Stoppers on 1800 333 000 with any information.
