Dalle was born in Brest, Finistère, France, as Béatrice Cabarrou. In 1985, she married the Painter Jean-François Dalle whom she divorced in 1988.

Working as a model when she met filmmaker Jean-Jacques Beineix, Beineix cast her in the lead role of the 1986 film 37°2 le matin (later released in the UK and USA as Betty Blue) which received BAFTA and Oscar nominations for Best Foreign Language Film, and made a star of Dalle.

She went on to appear in a series of major roles in French films, including the 1989 film Chimère, which was entered into the 1989 Cannes Film Festival.

She starred in Jim Jarmusch's Night on Earth in 1991. In 1997, she was cast in The Blackout, her first film made in the United States.

In 2001, Dalle appeared in the controversial film, Trouble Every Day, in which she played a vampire. More recently, she starred in the 2007 film À l'intérieur, in which she played a cruel psychopath stalking a pregnant woman.

Dalle's personal life has been controversial. She has been arrested on several occasions for shoplifting, drug possession and assault. In January, 2005, while making a film about prison life in Brest, Dalle met Guenaël Meziani, serving a 12-year prison sentence for assaulting and raping his ex-girlfriend. She married him after 24 one-hour visits, and spoke on his behalf at hearings for his early release. However, according to a 2015 profile of Dalle, she said the marriage was "a complete disaster" once Meziani was released from prison, and their divorce was apparently finalized in July 2014. She was also at one time in a relationship with Joeystarr.

Interviewed on the French TV programme Divan in 2016, Dalle said that, when she used to work in a Morgue, she and friends sold body parts of corpses. She also admitted that, while on acid, she once ate a dead man's ear.