Local media report that Craig Lawson of Courtland, Ont., pleaded guilty Tuesday in a Genesee County court before his trial was scheduled to begin.
Police say Lawson punched Jason McNeil in the head during a Kid Rock concert last July 5 at Darien Lake Theme Park.
McNeil, a native of nearby Alden in neighbouring Erie County, lives in Tuscaloosa, Ala., and was back home for a visit when he attended the concert.
He spent several weeks in a coma before being released from the hospital.
Lawson will be sentenced in August to up to a year in jail.