Wesolowski was born in Australia, and is of Polish descent through his grandfather. Wesolowski received international acclaim at the end of the 2004–05 season after competing for Australia in the FIFA World Youth Championship and was labelled "a star in the making" by the Australian Football Federation. Wesolowski was called up to the Australian national team on his 19th birthday for the 2007 Asian Cup qualifier against Kuwait, but was withdrawn from the squad days later after consultation with medical staff from both parties 'on precautionary grounds'. On 6 November 2007, he was called up to the national team for a friendly match against Nigeria on 17 November, but was an unused substitute as Australia won 1–0.