He became well known after roles in several French films such as Un, deux, trois, soleil (1993), which garnered him the César Award for "Most Promising Actor", The Horseman on the Roof (1995), and The Chambermaid on the Titanic (1997).

He has also appeared in Hollywood-produced features, including the drama Before Night Falls (2000), the erotic thriller Unfaithful (2002) and playing the role of a French drug lord in the action-crime-thriller S.W.A.T.

[4] In 1996/7 he appeared in Bertrand Blier's romantic comedy My Man (Mon Homme) alongside Anouk Grinberg, Gérard Lanvin, and Valeria Bruni Tedeschi.

Martinez portrays a French foundry worker who wins a strongman contest and the prize of a trip to view the departing maiden voyage of the ill-fated Titanic.

[6] The film was well-received; Mick LaSalle of the San Francisco Chronicle praised what he felt was a rare honest portrayal of male sexuality by Martinez.

Martinez first came to mainstream attention in Hollywood films with his performance in Julian Schnabel's Before Night Falls (2000) opposite Javier Bardem and Johnny Depp.

[11] On 22 November 2012, Martinez was treated at a Los Angeles hospital after being injured in a physical altercation with Canadian model Gabriel Aubry, Berry's former partner and father of her daughter.