Police responded to the incident at Armadillos Beckenham on Colombo Street around 9.15pm on Friday following reports of an injured person at a premises.
Senior Sergeant Anton Ten Hove said police were initially advised the male victim collapsed inside the bar.
“The male victim has received what appears to be a stab wound not in the bar. He arrived at the bar after having been allegedly stabbed,” he said.
The victim has been transported to hospital and enquiries to establish what happened are ongoing, police said.
The incident was reported opposite the Christchurch South Police Station.