RCMP say the man, who was 33, was injured last night at around 11:23 p.m. near a campground 30 kilometres west of Rocky Mountain House.
Police say his friends tried to revive him but the man was pronounced dead at the scene by emergency medical technicians.
His name has not been released.
RCMP say the man was not wearing a helmet and alcohol is believed to have been a factor in the rollover.
Police say people should wear approved safety equipment when driving ATVs and note that it is against the law to operate any vehicle while impaired by drugs or alcohol.