The party was taking place at a house in the small town of Viskafors and an alarm was raised to the emergency services at 10.45 pm.
When police arrived at the scene the man was in a serious condition. He was taken to hospital in Borås where he later died.
A 35-year-old man has been arrested and questioned overnight on suspicion of murder.
Police have taken witness statements from friends and family attending the party but it is not yet clear whether the incident took place inside or outside the house.
Reports suggest an argument was the cause of the incident.
”A group of families were at the party and had fallen out over something which which led to the stabbing,” Thomas Andersson from Borås police told newspaper GT.
A forensic investigation is underway at the house where the party took place.