Police were called at around 7pm on Sunday 22 July following reports of an assault at the Kings Arms in Lord Street, Fleetwood.
According to police reports, a man, believed to be in his 60s, was found unconscious at the scene.
After being attended to by emergency services, the man was taken to Blackpool Victoria Hospital for treatment but was later pronounced dead.
Detective chief inspector Gareth Willis of Lancashire Police said: “My thoughts are with the family and friends of the man who has sadly died.
“We are at the very early stages of our investigation and would appeal to anyone with information, or who saw what happened, to come forward if you have yet to speak to police.”
Lancashire Police are conducting an investigation and have appealed for information, which can be given by contacting police on 101 and quoting log 1327 of 22 July.
While a 62-year-old man from Fleetwood has been arrested on suspicion of murder and is currently in custody, police have appealed for anyone with information to contact police.