Brosnan made his Kerry Senior debut against Louth in 2000.[1] He won the All-Ireland Senior Football Championship title with Kerry on three occasions - 2004,[1] 2006[1] and 2007. The 2004 and 2006 finals were played against Mayo, while the 2007 final was against Cork. In the 2006 tie, Brosnan came on as a substitute in place of Tomás Ó Sé against Mayo and scored 1-01. In the 2007 game he scored one point and set up another. In 2008, Kerry again reached the All-Ireland final, but lost to Tyrone, and there was some criticism of the decision to select Brosnan.[3] He also won two National League titles (2004 and 2006)[1] and five Munster Championship medals (2001, 2003, 2004, 2005, 2007, 2011, 2013) with Kerry. Brosnan retired from Inter-county football in December 2013.[4][5]