As a walk-on, Bieber played college baseball for the UC Santa Barbara Gauchos, and was selected by the Indians in the fourth round of the 2016 MLB draft.

He made his MLB debut with Cleveland in 2018, was named an All-Star in 2019 and 2021, and received the American League's 2020 Cy Young Award.

He was recruited to play college baseball at University of California, Santa Barbara as a walk-on and did not receive much attention from many other programs.

[6][7] Bieber signed and made his professional debut with the Mahoning Valley Scrappers, where he spent the whole season, posting a 0.38 ERA in 24 innings.

[8] He spent 2017 with the Lake County Captains, Lynchburg Hillcats, and Akron RubberDucks, pitching to a combined 10–5 record with a 2.86 ERA in 28 starts between the three teams.

For the season, he received mention for the Cy Young Award voting for the first time, placing fourth in the American League.

Bieber struck out 14 batters in six innings in a 2–0 victory, setting a team record for most strikeouts by a starting pitcher on Opening Day.

Upon reaching 50 innings for the season, Bieber had tallied 84 strikeouts, the most by a starting pitcher in MLB history in that span, according to the Elias Sports Bureau.

[22] For the 2020 season, Bieber became the first pitcher since Justin Verlander (who won in 2011 with the Detroit Tigers), to capture the American League pitching triple crown (8 wins, 1.63 ERA, 122 strikeouts) as the AL leader in each of the three categories.

[24] In the 2020 American League Wild Card Series against the New York Yankees, Bieber allowed seven runs on nine hits in 4+2⁄3 innings, and the Indians were defeated 12–3.

[28] After the season, Bieber won the Gold Glove Award, along with teammates Steven Kwan, Andrés Giménez, and Myles Straw.

However, on April 6, 2024, it was announced that Bieber would undergo Tommy John surgery to repair his ulnar collateral ligament, ending his season.