A 32-year-old man, who has not been named, died outside the Studio Sport Bar in Hexham from head injuries at about 04:00 GMT .
A 25-year-old man has been arrested and is currently in custody.
Det Insp Dave English from Northumbria Police said the "tragic death" was being treated as an "isolated incident" and is appealing for witnesses.
A man has been arrested on suspicion of murdering a man who died after being found unconscious.