O'Hearn played with USSDA side PA Classics from 2011,[1][2] before going to play college soccer at Georgetown University in 2017. O'Hearn played three full seasons with the Hoyas, making 62 appearances and as a rookie was named to the Big East All-Freshman Team. The Big East season was cancelled in 2020 due to the COVID-19 pandemic.[3]
On November 30, 2020, it was announced that O'Hearn had signed with USL League One side New England Revolution II ahead of their 2021 season.[5] On January 21, 2021, O'Hearn was drafted 38th overall in the 2021 MLS SuperDraft by Minnesota United.[6] However, he was not signed by Minnesota and remained with New England. His MLS rights were later traded to Toronto FC in March 2022.[7]
On April 10, 2021, O'Hearn made his professional debut, starting against Fort Lauderdale CF in a 1–0 win.[8]
