Police arrested several people after being called to respond at 2.40am to a dispute at Club 3000, located in a rural area known as Lätti, north of the city of Bern.
Officers found a seriously injured man who was transported to hospital, where he died from his injuries, police said in a statement issued on Wednesday.
Neither the identity nor the age of the victim were immediately known.
An argument between several people broke out in the premises of a restaurant at the club, police said.
Another man was injured in the brawl but his injuries were not life-threatening, police said.
With a criminal investigation under way, Bern police remain tight-lipped about the details of the fight and how the man who died received his injuries.
The 20 Minuten newspaper described the Club 3000 as a “sex club” and a “brothel”.
It is located in a remote village surrounded by potato fields, the newspaper said.
“Neither the victims nor those arrested are employees of the club,” cantonal police spokesman Christoph Gnägi told 20 Minutes.
The club’s activities are apparently discreetly carried out without any direct impact on the neighbourhood, the newspaper indicated.
“We have little interest in what is going on in the brothel,” a local resident is quoted as saying.
“We did not hear the police operation,” another neighbour said.
On the internet, the club advertises the services of 10 to 30 women from different countries who “serve” customers in rooms at an adjacent “Motel Paradiso”.
Google map above shows location of club.