Career
He has 5 All-Irelands, 3 NFLs, 7 Munster Championships, 1 County Senior Championship, 1 Senior Club County Championship, 1 County U21 Championship, 1 County Intermediate Championship and 3 All Stars. A Garda Síochána member, he played for Kerry's U21 team in 2000 and 2001. He debuted for the Kerry senior team in the 2003 League campaign and in the Championship versus Clare in 2004.
He repeated the performance in the 2006 All-Ireland Final against the same team. Kerry dominated, and Mayo were easily defeated by a score of 4-15 to 3-05, and O'Mahony picked up the RTÉ Man of the Match Award for scoring 2 points and marking Ciarán McDonald. O'Mahony again played an important part as Kerry reached the 2008 All-Ireland Final, defeating Cork in the semi-final.
Many Cork fans were angered by O'Mahony's role in the sending off of Cork forward Donnacha O'Connor. His collapse to the ground after O'Connor slapped him was described as a deliberate dive. In 2010, O'Mahony took a break from inter-county football after Kerry's NFL campaign for personal reasons.
He, however, returned to the panel for the Championship. In 2005, following the All-Ireland final loss to Tyrone, O'Mahoney tested positive for a banned steroid, salbutamol. However he faced no censure because salbutamol is found in asthma inhalers, and he was thus granted a therapeutic use exemption.
He once played on for more than 40 minutes in a club final with a broken leg, scoring two points.