Born in Belfast,[4] Kearns began his grassroots career in the youth team of his local club St Oliver Plunkett.

[6][7] After being released by West Ham in May 2010, Kearns signed for Dundalk of the League of Ireland Premier Division in August on a short-term contract.

[3] Kearns played in Dundalk's seven matches in their run to the Setanta Sports Cup Final, where his team lost 2–0 to Shamrock Rovers.

[3] Kearns signed a three-year contract with English Championship club Peterborough United on 30 August 2011 for an undisclosed fee.

[9] He made his debut for Peterborough on 24 September, in a 1–0 defeat against his former club, West Ham United, coming on as an 89th-minute substitute for Lee Frecklington.

[10] Kearns signed for League Two club York City on 4 October 2012 on a one-month loan,[12] making his debut two days later as a 66th-minute substitute in a 0–0 draw at home to Rotherham United.

[13] Kearns signed for League Two team Chesterfield on 11 March 2014 on a one-month loan[18] and made his debut that day as a 66th-minute substitute for Jimmy Ryan in a 1–1 draw away to AFC Wimbledon.