Pierce O'Leary losses
Over 7 years as a professional, Pierce O'Leary has compiled a 19-1 (11) record, including eight title fights. His only loss came in a title fight against Mark Chamberlain.
1. Pierce O'Leary loses to Mark Chamberlain via KO
On August 1, 2026 Pierce O'Leary defended his IBO World super lightweight title against Mark Chamberlain. O'Leary was 26 years old with a record of 19-0, and Chamberlain was 27 with a record of 17-1-1. O'Leary was on an undefeated 19-fight winning streak. Chamberlain stopped O'Leary via TKO in the 10th round. Lost the title. Lasted into the 10th round.