He played college football at Ohio State, where he was a two-time unanimous All-American, one of only eleven players in Big Ten Conference history, and the Fred Biletnikoff Award winner in 2023.

[21] As a freshman in 2021, he received limited playing time behind future first-round NFL draft picks Garrett Wilson, Chris Olave, and Jaxon Smith-Njigba.

Having only had five receptions for 68 yards in the regular season, he would make his first career start in the 2022 Rose Bowl after Wilson and Olave declared for the 2022 NFL draft.

[28][29] In his first game as the team's top receiver, Harrison caught seven passes for a then career-high 184 yards and three touchdowns in a victory over Arkansas State.

[30] Following a relatively unimpressive first two conference games, Harrison returned to form against Michigan State, catching 7 passes for 132 yards and three touchdowns.

[35][36] Despite the loss to Michigan, Ohio State earned a bid to the College Football Playoff where they would play the defending national champion Georgia Bulldogs in the Peach Bowl.

[38][39][40][41] Harrison shone in the first half of the contest, catching five passes for 106 yards and two touchdowns, helping Ohio State gain a 35–24 lead.

[45][46] At the conclusion of the season, Harrison was voted a unanimous All-American and named the Richter–Howard Receiver of the Year after recording 1,263 yards and 14 touchdowns.

[49][50][51] He finished fourth in the Heisman Trophy voting and won the 2023 Fred Biletnikoff Award after recording 1,211 yards for 14 touchdowns, the latter being tied for third most in the FBS.