Police on North Road stopped a car at 12.15am with two badly injured men travelling in it.
One had been stabbed in the eye and the other had been stabbed in the arm, Detective Sergeant Chris Henderson said.
The two men, aged 53 and 37, were admitted to Dunedin Hospital for treatment.
Neither had "a reasonable explanation" about how they had received the injuries, Det Sgt Henderson said.
Police are investigating activities at the house where one of the men lived and a cordon had been put in place as a precaution, Detective Henderson said.
There was a "substantial amount of blood" at the address and windows at the house had been smashed, he said.