Despite being projected to be selected as high as the fourth round, Crowell did not get drafted. On May 10, 2014, he signed as an undrafted free agent with the Cleveland Browns and was given a $10,000 signing bonus immediately.
On September 7, 2014, Crowell made his NFL debut, running for 32 yards on 5 carries and two touchdowns in a 30–27 loss to the Pittsburgh Steelers. On September 14, 2014, Crowell ran for 54 yards on 11 carries in a win over the New Orleans Saints, the Browns' first home opening win in a decade. On September 21, 2014, Crowell scored his third touchdown of the season against the Baltimore Ravens. Crowell and rookie running back Terrence West each scored a rushing touchdown, the first time two Browns rookies had done that in a single game since 1979 (Dino Hall and Pat Moriarty). On October 12, 2014, Crowell ran for 77 yards on 11 carries and a touchdown against the Pittsburgh Steelers. On November 6, 2014, Crowell scored his 4th touchdown of the season against the Cincinnati Bengals. On November 16, 2014, Crowell ran for 61 yards on 14 carries against the Houston Texans. On November 23, 2014, Crowell ran for a season-high 88 yards on 12 carries and two touchdowns against the Atlanta Falcons. On December 7, 2014, Crowell scored his eighth touchdown of the season against the Indianapolis Colts. He finished the season playing 16 games for 607 rushing yards on 148 attempts (4.1 yards per attempt) and 8 touchdowns plus 9 receptions for 87 yards while starting 4 games. Among rookies, Crowell ranks fifth in rushing yards, only one of nine rookies to break 500 yards, and one of five to break 600 yards. Crowell was ranked second in rushing touchdowns among rookies, just behind Cincinnati Bengals' running back Jeremy Hill.