Renier trained at the Conservatoire Royal in Brussels and started his professional acting career in 1995, appearing in many stage productions of both classical and modern drama. Renier's first full-length film was Miss Montigny in 2004.
He became widely known in Belgium in 2006 through his role in the first series of the television drama Septième Ciel Belgique. He then played opposite Isabelle Huppert and his half-brother Jérémie in the film Nue Propriété, and has since appeared in other roles including the lead part of Yves in the 2008 Nés en 68. For his role in Private Lessons (Élève libre), Renier was nominated for Best Supporting Actor at the 1st Magritte Awards.