The son of Tom and Barbara, Jahn attended Jesuit High School in Carmichael, California, where he played soccer.

Jahn was selected as the 15th pick in the 2013 MLS Supplemental Draft by his local team, the San Jose Earthquakes, on January 22, 2013.

[1] On March 3, 2013, Jahn made his debut for the Earthquakes at Buck Shaw Stadium in the opening game of the season by coming on as a substitute in the 83rd minute for Ty Harden.

On a subsequent play, he headed the ball into the hand of Roy Miller, setting up the winning penalty kick by Chris Wondolowski to complete a 2–1 comeback victory.

[11] On February 22, 2021, Jahn joined USL Championship side Orange County SC, technically on loan from Atlanta United, although he had recently been waived by the MLS club.