Cassel was born Vincent Crochon in Paris, France, to Sabine Litique, a journalist, and French actor Jean-Pierre Cassel (born Jean-Pierre Crochon).
He is married to Italian actress Monica Bellucci, with whom he has two daughters, Deva (born 12 September 2004) and Léonie (born 21 May 2010).
His brother Mathias is a rapper with the group Assassin under the name "Rockin' Squat". His half-sister, Cécile Cassel, is an actress.
He has a passion for Capoeira and displayed his talent in the movie Ocean's Twelve. Besides his native French, Cassel speaks English, Brazilian Portuguese, Italian and basic conversational Russian which he learned for his role in Eastern Promises.