Pfaadt attended Trinity High School in Louisville, Kentucky, and played college baseball at Bellarmine University.
[3] The Arizona Diamondbacks selected Pfaadt in the fifth round of the 2020 Major League Baseball draft.
[5] He made his professional debut in 2021 with the Visalia Rawhide and was promoted to the Hillsboro Hops and Amarillo Sod Poodles during the season.
[7] In 2022 in 29 starts split between Double-A Amarillo and the Triple-A Reno Aces, he was 11–7 with a 3.83 ERA, and led the minors in innings pitched, with 167, as well as strikeouts, with 218.
On May 3, 2023, Pfaadt was selected to the 40-man roster and promoted to the major leagues for the first time to serve as the starting pitcher against the Texas Rangers.