The crash left one of the men fighting for his life in Dunedin Hospital's intensive-care unit and the other in a serious condition in another ward.
Both men were on the motorcycle when it crashed into a pole in Pine Hill Rd about 5.40pm.
Sergeant Ed Baker said it was believed neither man was wearing a helmet.
It appeared the motorcycle was travelling south when it failed to take a right-hand bend and collided with a pole on the left side of the road, near Hislop St, he said.
Both men are in their mid-20s.
It was unclear last night which man was driving the motorcycle when it crashed, Sgt Baker said.
The CIB and serious crash unit were investigating the crash.
• Detours were in place last night after a male walking along State Highway 1 between Timaru and Temuka was struck by a vehicle and killed about 7.35pm. Two other people sustained minor injuries, NZPA reported.
Further details were unavailable.
