As a true freshman at Michigan, Peppers appeared in three games, making one start. In his first career start against Appalachian State, he recorded two tackles and returned one punt for six yards. Because of an injury he sustained against Appalachian State, Peppers was redshirted for the remainder of his freshman season. Following the 2015 season, Peppers was named the Big Ten Thompson-Randle El Freshman of the Year, and named to the All-Big Ten defensive first-team, by both the coaches and media, and the All-Big Ten special teams second-team by coaches. He was also named a Second-Team All-American by CBS Sports and Sports Illustrated. He was also named to the Freshman All-America Team by Football Writers Association of America. He was a finalist for the Paul Hornung Award. In 12 games, Peppers played a combined 986 snaps this season, with 50 coming on offense, 765 on defense and 171 on special teams. On defense, he registered 45 total tackles, 5.5 tackles-for-loss and 10 pass breakups. On special teams, he returned all 17 punts on the season for 194 yards, an average of 11.4 yards per return. Peppers has returned eight kickoffs for 223 yards, an average of 27.9 yards per return, on a unit that ranks second in the FBS with 28.41 yards per kick return. On offense, he added eight catches for 79 yards with 18 rushes for 72 yards and two touchdowns. Peppers has gained 568 all-purpose yards on the season, an average of 47.3 yards per game, ranking fifth on the team.