As a true freshman in 2011, Carey rushed for 425 yards on 91 carries with six touchdowns. In 13 games of his sophomore season in 2012, he rushed for 1,929 yards on 303 carries with 23 touchdowns, which broke the Arizona single-season record for both rushing yards and rushing touchdowns. On November 10, 2012 Carey set the Pac-12 record for rushing yards in a game with 366. On December 11, 2012 Carey was named a 2012 consensus All-American at the running back position.
In January 2013, he pleaded not guilty to misdeameanor assault and disorderly conduct charges stemming from an alleged domestic violence incident involving his pregnant ex-girlfriend. Charges were dropped in June.
Carey served a one-game suspension to start the 2013 football season. During the season he set a school record for rushing yards and rushing touchdowns. He finished the season with 1,885 yards on 349 carries and 19 touchdowns and was a consensus All-American for the second straight season.