Denayer competed for the national team at the 2008, 2012 and 2016 Olympics, winning a silver medal at the Rio Olympics. With Belgium he won the silver medal at the 2013 European Championship on home ground in Boom, and again at the 2017 European Championships in Amsterdam. He also tasted World Cup success with Belgium in 2018. In 2019, he was a part of the squad which won Belgium its first European title. On 25 May 2021, he was selected in the squad for the 2021 EuroHockey Championship. He was the captain of the Belgian team which won the gold medal at the 2020 Summer Olympics.