In addition to the guilty plea, Jonathan Roy offered a $5,000 check to charity.
The Hall of Famer was coaching behind the bench when his son, a goalie with the Quebec Remparts, skated across the rink during a junior game in March 2008 to pummel an opposing goalie.
That beating prompted numerous politicians to enter a debate over what could be done to curb violence in hockey. Even Prime Minister Stephen Harper waded in on the issue.
Roy had been trying to get the case tossed out but was rebuffed by a judge. Roy argued he was being prosecuted based on new provincial rules that weren't in place when the attack occurred.
Under rules introduced in July 2008, Quebec's Office of Public Prosecution toughened a 30-year-old regulation that made assault charges possible for a hockey player when the incident resulted in injury.