As a member of the senior men's Lithuanian national basketball team, Mačiulis played at the EuroBasket 2007, where the Lithuanians claimed bronze medals. In the 2008 Summer Olympics, he took 4th place. In the 2010 FIBA World Championship, he won a bronze medal. In the EuroBasket 2013, Lithuania was runner-up, and Mačiulis played one of the best games of his career with national team, in the semi-finals against Croatia.