A New Zealand national captain and second-row forward, Kearney's club football career, which spanned from the early 1990s to the mid-2000s, was played for the Randwick Kingfishers, Western Suburbs Magpies, Auckland Warriors, Melbourne Storm (with whom he won the 1999 NRL Premiership), and Hull F.C.

[6] Kearney was selected for the New Zealand team to compete in the end of season 1999 Rugby League Tri-Nations tournament.

Having won the 1999 Premiership, the Melbourne Storm travelled to England to contest the 2000 World Club Challenge against Super League Champions St Helens R.F.C., with Kearney playing at second-row forward in the victory.

In 2002 Kearney missed the series-deciding match against Great Britain as he had to rush back home to Melbourne to be with his sick five-year-old daughter, who needed emergency surgery.

[3] In 2006 Kearney retired from playing and returned to Australia to take up a role as assistant coach at his old club, the Melbourne Storm, under Craig Bellamy.

In 2008 Kearney was appointed as the New Zealand national rugby league team head coach on a two-year contract.

[11] Following this achievement, he was appointed an Officer of the New Zealand Order of Merit, for services to rugby league, in the 2009 Queen's Birthday Honours.

In the 2010 post-season Kearney was announced as Daniel Anderson's replacement as head coach of the Parramatta Eels for three years beginning in 2011.

In 2011 he failed to coach the Parramatta NRL team to any success, with the Eels achieving just 6 wins and 1 draw in 24 matches, and only just missing out on the wooden spoon when they beat the Gold Coast Titans in the last game of the regular season.

In March 2015, Kearney signed a new deal to remain as coach of the Kiwis until the conclusion of the 2017 Rugby League World Cup.

[25] On 20 June 2020, Kearney was sacked by the New Zealand Warriors, due to poor results, and was replaced by his assistant coach Todd Payten.