Son of former Ireland prop Des, Luke made his senior Leinster debut in September 2006. At the end of the 05/06 season he was studying for his Leaving Cert at Blackrock and helping them to a 65th Schools Cup final win.

Fitzgerald was capped by the Leinster and Ireland Schools teams and was part of the Ireland Schools XV that completed a clean sweep of wins in 2005, winning the Irish Examiner Young Rugby Player of the Year award that same year.

He made his debut for Ireland in the final game in Lansdowne Road against the Pacific Islanders in 2006.

Fitzgerald's pace, eye for a gap and tackling saw him become an integral part of Ireland squads including the 2009 Grand Slam.