Police said the man was assaulted on Friday night in the car park of The White House, a Wetherspoon pub in the Leicestershire village of Scraptoft.
Emergency services were called to the pub at 22:10 BST and the man was taken to hospital where he died.
The 23-year-old man who was arrested is in police custody.
Tributes have been left near the door of the pub.
Police have appealed for anyone who witnessed the assault or events leading up to it to contact them.
A man has been arrested in connection with the death of a man who was assaulted in a pub car park.