Lončarić joined GNK Dinamo Zagreb in 1994,[1] aged just eight and made his breakthrough to the first-team squad for the 2005–06 season.

After Dinamo, he played at CS Gaz Metan Mediaș, FK Željezničar Sarajevo, NK Osijek, HŠK Zrinjski Mostar and Tromsø IL, before retiring from football in August 2018 at the age of 31.

[2] However, following the club's signing of German goalkeeper Georg Koch in the summer of 2007, Lončarić once again found himself relegated to the bench and only appeared in two domestic league matches early in the season before sustaining an injury in a cup match in October 2007, which led to him being sidelined for most of the season and eventually losing his place as the club's second-choice goalkeeper to Ivan Kelava.

However, he was soon forced to take another lengthy break after renewing his injury in Dinamo's Europa League match against Ajax on 22 October 2009.

[2] His first competitive match after the injury break came on 31 July 2010 in a 2–1 defeat at home to Rijeka in the Croatian top flight, deputising for the injured Butina.

[3] Initially the club's second-choice goalkeeper, he made his league debut on 9 July 2016 in a 2–2 draw at home to Haugesund.

He made seven more appearances for the under-16 selection before debuting for the under-17 team in a friendly match against Czech Republic on 7 August 2002, aged just 15.