In 2015, Elliott began the season by rushing for over 100 yards in 10 straight wins, including 274 against Indiana on October 3 (the second most all-time by an Ohio State player). However, the team suffered a 14–17 loss to Michigan State on November 21, 2015, and Elliott announced that he would enter the 2016 NFL Draft. The following week, Elliott ran for 214 yards on 30 carries in a 42–13 Ohio State victory over rival Michigan in Ann Arbor, his fifth 200+ yard game. He ended his collegiate career with 149 yards and four touchdowns in a Fiesta Bowl win over Notre Dame.
Elliott finished his career at Ohio State on several leaderboards. He was second in career rushing yards with 3,961 and yards per game with 101.6 (both behind only Archie Griffin), had the second and third most rushing yards in a season, and five of the top 20 rushing yards in a game. His 43 rushing touchdowns was fourth most all time, and his 23 in 2015 was third most in a season. His twelve 100-yard rushing games in the 2015 season tied Eddie George for a school record, and the 22 he amassed over his career was again second only to Griffin (as was his streak of 15 consecutive 100-yard games from 2014–2015). He and George are the only Ohio State players with five 200-yard rushing games.