The Pirates assigned Bell to work out with the State College Spikes, but as the season was ending, he did not appear in a game with the Spikes in 2011. Bell participated in the Pirates' fall instructional league. Bell was ranked the 69th best prospect in baseball by MLB.com before the 2012 season. He made his professional debut in 2012 with the West Virginia Power of the Class ASouth Atlantic League. However, on April 24, 2012, Bell hit what would have been a double, but pulled up limping rounding first base, and was tagged out standing between first and second with an injury. Bell ended up having a partial tear of his meniscus, on the lateral part of the meniscus in his knee. Bell missed almost all of the 2012 minor league season, and was out longer than expected due to swelling in the injured knee. Bell again played for the West Virginia Power in 2013. He batted.279 with 13 home runs, 76 RBIs, and 37 doubles in 119 games. Bell opened the 2014 season with the Bradenton Marauders of the Class A-AdvancedFlorida State League, and appeared in the 2014 All-Star Futures Game. After hitting.335 with nine home runs and 35 RBIs for Bradenton in 84 games, the Pirates promoted Bell to the Altoona Curve of the Class AAEastern League on July 17. In 24 games for Altoona, he batted.287/.343/.309. After the season, he was named the FSL Player of the Year. The Pirates assigned Bell to the Arizona Fall League after the 2014 season, where he played exclusively as a first baseman, due to the Pirates carrying Andrew McCutchen, Starling Marte, and Gregory Polanco in their major league outfield. The Pirates assigned Bell to Altoona to start the 2015 season. He was chosen to represent the Pirates at the 2015 All-Star Futures Game. At the end of July, the Pirates promoted Bell to the Indianapolis Indians of the Class AAAInternational League. In 96 games for Altoona, he batted.307 with five home runs and 60 RBIs. He batted.347 with two home runs, 18 RBIs, and a.441 on-base percentage in 145 plate appearances with Indianapolis, and the Pirates added Bell to their 40-man roster after the season.
Pittsburgh Pirates
Bell began the 2016 season with Indianapolis. After batting.324 with a.407 on-base percentage in 83 games for the Indians, the Pirates promoted Bell to the major leagues on July 8. He made his MLB debut that night as a pinch hitter, and hit a grand slam in his second MLB at-bat on July 9. He was optioned back to Indianapolis on July 16, and recalled once again on August 20. In 128 at-bats for Pittsburgh, Bell batted.273 with three home runs and 19 RBIs. On February 1, 2017, Bell underwent left knee surgery, but did not go on the disabled list or miss any games. On September 4, 2017 Bell broke the National League record for most home runs by a rookie switch hitter, hitting his 24th of the season off of Jake Arrieta, in a 12–0 Pirates' rout of the Chicago Cubs He was one of three finalists for the 2017 Rookie of the Year award along with Cody Bellinger and Paul DeJong, and finished in third place in the balloting. Bell played 159 games, finishing with a.255 batting average, 26 home runs and 90 RBIs. On May 8, 2019, Bell became the fourth player in PNC Park history to hit a ball directly into the Allegheny River; the ball traveled 470+ feet with an exit velocity of 114+ MPH. Bell was elected to his first MLB All-Star Game on June 30, 2019. Bell also participated in the 2019 Home Run Derby where he was eliminated in the first round after hitting 18 home runs. On defense, in 2019 he had the lowest fielding percentage of all major league first basemen.