She was expelled from school when she was 16, after which she spend time in Rome with the Dolce Vita crowd, and then went to New York City to hang out with Andy Warhol's Factory crowd. She then began her career as a fashion model in Paris. She studied medicine, picture restoration and graphic design without achieving a degree. Before settling in London, she lived in Germany, in her native Rome, as well as in New York City, where she was involved with the Living Theatre, starring in the play Paradise Now, which featured onstage nudity, and Andy Warhol's Factory.
Pallenberg appeared in over a dozen films over a 40-year span. One of her first appearances was as The Great Tyrant in Roger Vadim's science fiction film Barbarella (1968) (although the character's voice was dubbed by Joan Greenwood,) and as the sleeper wife of Michel Piccoli in the film Dillinger Is Dead (1969), directed by Marco Ferreri.[8] She also had roles in the German crime thriller A Degree of Murder (1967) which featured music by Brian Jones, the cult film Candy (1968) as James Coburn's possessive nurse, Volker Schlöndorff's Michael Kohlhaas – Der Rebell (1969) which was filmed in Slovakia, and the avant-garde Performance (1970) in which she played the role of Pherber. The film was shot in 1968, but a nervous studio delayed its release.Pallenberg appeared in a documentary about the Rolling Stones, Sympathy for the Devil (1968), directed by French filmmaker Jean-Luc Godard. In a March 2007 interview, she related her encounters in Rome while La Dolce Vita (1960) was being filmed, with its director Federico Fellini, other filmmakers such as Luchino Visconti and Pier Paolo Pasolini, and with the novelist Alberto Moravia In 1985, for the video of "Wild Boys", Duran Duran used a clip of Pallenberg from Barbarella. She portrayed "The Queen" in the comedy-drama Mister Lonely by Harmony Korine, and played a character named Sin in Go Go Tales (both 2007).
In 1979, a 17-year-old boy, Scott Cantrell, shot himself in the head in Pallenberg's bed with a gun owned by Keith Richards, while at the South Salem, New York house shared by Richards and Pallenberg. The youth had been employed as a part-time groundsman at the estate and was involved in relationship with Pallenberg. Richards was in Paris recording with the Rolling Stones, but his son was at the house when the teen killed himself. Pallenberg was arrested; however, the death was ruled a suicide in 1980, despite rumours that Pallenberg and Cantrell had been playing a game of Russian roulette. The police investigation stated that Pallenberg was not on the same floor of the house at the time the fatal shot was fired.