Already at school, he proved himself in the acting field in school performances.

In 1997, at the age of 13, he made his debut in the TV movie Kissing Family. Two years later, he makes his film debut: in the adventure film for children "The Bear Runs Away". In 2001, he starred in Dennis Ganzel's teen comedy in the spirit of American Pie. — "Girls from above". After supporting roles in television series (Wolf's Law, Special Squad Cobra), in 2003 he again worked with Dennis Ganzel, playing the main role in the well-reviewed drama Death Academy. For this role, he won the Best Actor nomination at the Karlovy Vary International Film Festival. On February 14, 2006, the world premiere of the film "Red Cockatoo" took place. at the Berlin Film Festival, where Riemelt plays the role of Sigi, for which he receives the Bayerischer Filmpreis award; in the Best Young Actor nomination. In 2008, he again starred with Dennis Ganzel in the film “Experiment 2: Wave”. In 2009, he plays a student in the comedy The Thirteenth Term. In 2010, he once again worked with Ganzel in his film about vampires, “Taste of the Night.”

Riemelt has a daughter and a dog.