Jesse Allen Hahn was born on July 30, 1989, in Norwich, Connecticut, and grew up in Groton. He went to Fitch Senior High School, where he pitched alongside Matt Harvey. In his senior year, he had 65 strikeouts in 40 innings, with an impressive 0.17 ERA. He also threw a no-hitter and three one-hit games, earning honors like All-State and Pitcher of the Year. After high school, he joined Virginia Tech and played for the Hokies baseball team. He started several games as a freshman and continued to develop in his second year. In the summer of 2009, he played for the Chatham Anglers in the Cape Cod Baseball League, where he faced top college talent. In 2010, he injured his elbow and had Tommy John surgery, which ended his season and delayed his start in pro baseball.
Jesse Hahnwas picked by the Tampa Bay Rays in the sixth round of the 2010 MLB draft out of Virginia Tech and signed for about $525,000. He needed time to recover from elbow surgery (Tommy John) and did not make his professional debut until 2012. In January 2014, he was traded to the San Diego Padres. Hahn made his major league debut on June 3, 2014. He finished that year with a 7–4 record and a 3.07 ERA over 73⅓ innings pitched for San Diego.
In December 2014, the Padres traded Hahn to the Oakland Athletics. During his time in Oakland, he appeared in parts of three seasons starting games. In 2015 he went 6–6 with a 3.35 ERA, though injuries and inconsistency limited him to 38 starts in those three years.
Ahead of the 2018 season, Hahn was traded to the Kansas City Royals. Injuries followed and he missed all of 2018 due to elbow problems. In 2019 he pitched only sparingly in the majors before re-signing with KC at year-end.
The 2020 season proved a career high point. Hahn appeared in 18 relief outings and posted an outstanding 0.52 ERA with 19 strikeouts in 17.1 innings, setting a modern mark for opponents’ batting average in Royals history. He suffered a shoulder issue in 2021 and went on injured list, missing most of that season.
Hahn did not play in MLB again until 2025. In January he signed a minor league deal with the Dodgers and pitched at Triple-A Oklahoma City before being released in August after posting a 4.29 ERA in about 50 innings. Soon after, he re-signed with the Seattle Mariners on a minor-league deal and received a call-up in April 2025. He made two relief appearances, pitching four innings with one unearned run, three strikeouts, and four walks, before clearing waivers and returning to Triple-A Tacoma. Over his MLB career through April 2025, Hahn has appeared in 85 major-league games (50 starts). His record stands at 19–22, with a 4.17 ERA, 244 strikeouts in about 316 innings, and a WHIP near 1.35.