Addison announced his decision on Instagram, writing: "To all my Pitt boys and my West coast men thank you for making this journey memorable forever.. See you on Sundays."
His decision had been expected for weeks after he opted out of USC's appearance in the Cotton Bowl against Tulane.
ESPN lists Addison as the No. 2 draft-eligible wide receiver and the No. 14 overall prospect.
Addison had 59 receptions for 875 yards and eight touchdowns in his lone season at USC, leading the team in all three categories. He had four 100-yard-receiving performances for the Trojans, including a season-high 178 yards on 11 catches in a road win over rival UCLA.
Addison's numbers declined from the 2021 season, when he had a Pitt-record 100 receptions for 1,593 yards and 17 touchdowns, which tied for the FBS lead. The 6-foot, 175-pound Addison started eight games as a true freshman in 2020, recording 60 receptions for 666 yards and finishing as the runner-up for ACC Rookie of the Year.
Addison announced in May that he would transfer to USC, where he joined quarterback Caleb Williams, who went on to win the Heisman Trophy last season. His decision encapsulated the impact of the new one-time transfer rule in college football, which allows underclassmen to transfer once without sitting out a season, and the impact of name, image and likeness earning potential.