Harte made his senior debut for Ireland in August 2006 in a Celtic Cup game against France. Harte's brother, David, and his sister, Emer, also made their senior international debuts on the same day. Harte was a member of the Ireland teams that won the 2009 Men's EuroHockey Nations Trophy and the 2011 Men's Hockey Champions Challenge II. He also helped Ireland win Men's FIH Hockey World League tournaments in 2012, 2015 and 2017. On 1 June 2017, Harte made his 200th senior appearance for Ireland in a 2–2 with Pakistan. He marked the occasion by scoring from a penalty corner. Harte was also a member of the Ireland team that won the bronze medal at the 2015 Men's EuroHockey Nations Championship. He represented Ireland at the 2016 Summer Olympics and at the 2018 Men's Hockey World Cup.