Detectives are looking at a possible drugs link to the death of the man at a premises in the town's Kenlis Street area.
Three men, one man in his 40s and two men in their 20s, have been arrested in connection with the death.
Two other men were taken to hospital for treatment, one of them currently remains there.
He is said to be in a stable condition.
Police have asked for anyone with information about the incident to contact them.
Police are investigating the sudden death of a man, aged in his 20s, in Banbridge on Thursday evening.