His biological father, Michel Têtard, was a lyricist who had an affair with Dewaere's mother, Mado Maurin, who was married to Pierre-Marie Bourdeaux.

At the age of 17, Dewaere learned that he was not the biological child of his mother’s ex-husband, Pierre-Marie Bourdeaux, but that of conductor and singer Michel Têtard.

A year earlier, he had met his first wife, Sotha, an actress who co-founded the Café de la Gare, an experimental theatre.

[citation needed] From 1968, he collaborated with the Café de la Gare, where he met Miou-Miou and Gérard Depardieu, with whom he made a breakthrough after many secondary roles in various films, in the scandalous comedy Going Places.

She left Dewaere for singer Julien Clerc, shortly before the shooting of F...like Fairbanks, in which both play a couple in separation.

He consolidated his status as a savage and ruthless actor in Alain Corneau’s cult film Série noire (1979).

Shortly before the release of Paradis Pour Tous (1982), a black comedy where his character tries to commit suicide, the actor shot himself in his house in Paris.

[citation needed] In 1975, Dewaere received the Crystal Star of the Best Actor for The Best Way to Walk, shared with Patrick Bouchitey.