Mark C. Wells, 26, pleaded guilty Monday to killing James Schickling, 49, on June 4 during a fight at a wedding reception for the victim's niece.
Wells, a close friend of the groom, was charged with homicide. He told the court Monday that he threw the punch and was not provoked.
Authorities said the fight began as an argument between family, friends and members of the wedding party. Schickling was standing nearby but had not been involved in the fight at the hotel bar when Wells punched him in the head, police said.
He fell to the floor and never regained consciousness before he died a day and a half later, police said. The cause of death was blunt force trauma to the head.
Wells of Schnecksville is free on $200,000 (EUR149,555) bail and is scheduled to be sentenced in June. He faces a maximum sentence of 2 1/2 to five years in prison.
"I think he got caught up in the moment and made a bad decision that he'll regret for the rest of his life," defense lawyer John J. Waldron said.
Schickling's family expressed mixed feelings about the plea.
"It's a relief that we don't have to go through a long trial, but it's also frustrating when you find out somebody killed somebody unprovoked and the maximum sentence is five years," said Mark Hood, a relative.
On January 15, it was reported that the Russian government began to develop sanctions against several officials at the World Anti-Doping Agency (WADA)