Nemes was born in Budapest as the son of a Jewish mother and the Hungarian film and theatre director András Jeles. He moved to Paris at the age of 12. Nemes became interested in filmmaking at an early age and began filming amateur horror films in the basement of his Paris home. After studying History, International Relations and Screenwriting, he started working as an assistant director in France and Hungary on short and feature films. For two years, he worked as Béla Tarr's assistant during the filming of The Man from London.