He became a fixture with the Red Devils from his debut on 30 April 2001 in a friendly against the Czech Republic. National team manager René Vandereycken made him captain, but there was no room for the aging Simons in 2011 in the team of Dick Advocaat. Despite that, Leekens and Wilmots later called him up again. He was the first Red Devil to achieve 100 caps on 16 October 2012. Simons excelled in simplicity, first as defensive midfielder, and later as central defender. The less you noticed him, the better his match. He was a last-minute call up for the match against Estonia on 13 November 2016. He was brought on for seven minutes and became the oldest Red Devils player in an official match at 39 years, 11 months, and 2 days of age.