Peellaert was born into an aristocratic family, but left home at an early age. He studied fine arts in Brussels, and became heavily influenced by American and British pop culture, film noir and pulp literature, before making his debut as a decorator for theaters and comic strip artist.
His style was influenced by psychedelic art and Pop Art. He moved to Paris, where he worked variously in advertising, set design for the casino and the Crazy Horse nightclub, film and television. His comic strip, Les Aventures de Jodelle, was published in 1966 in the controversial French magazine Hara-Kiri. The protagonist, Jodelle, was modelled after singer Sylvie Vartan. Peellart's second comic strip heroine, Pravda, made her debut in 1968 and was modelled after singer Françoise Hardy.
In 1973, he collaborated with British rock journalist Nik Cohn on the best-selling book Rock Dreams, which reportedly sold a million copies after it was published the following year. The book consisted of Peelaert's visual illustrations which celebrated and exaggerated the rebel heritage of pop music and, particularly, rock and roll, with commentary by Cohn. Many of the original artworks were bought by actor Jack Nicholson.
After the success of Rock Dreams, Peellaert became perhaps best known for his rock album covers. He designed covers for The Rolling Stones (It's Only Rock 'n' Roll),David Bowie (Diamond Dogs), Étienne Daho (Pour nos vies martiennes), Lio (Wandatta), and others.
He painted in a very photorealistic style and often used pastel. The album cover of David Bowie's Diamond Dogs (1974) met with controversy. The cover art features Bowie as a striking half-man, half-dog grotesque. It was controversial as the full painting clearly showed the hybrid’s genitalia. Very few copies of this original cover made their way into circulation at the time of the album's release. According to the record-collector publication Goldmine price guides, these albums have been among the most expensive record collectibles of all time, as high as thousands of US dollars for a single copy. The genitalia was quickly airbrushed out for the 1974 LP’s gatefold sleeve, although the original artwork (and another rejected cover featuring Bowie in a cordobes hat holding onto a ravenous dog) was included in subsequent Rykodisc/EMI re-issues.
Peellaert also designed film posters for films like Taxi Driver (by Martin Scorsese), Short Cuts (by Robert Altman), L'argent (by Robert Bresson), Paris, Texas and Wings of Desire (by Wim Wenders). He also designed programme titles for television shows on the French TV channel Antenne 2 in 1982.
Peellaert and Cohn collaborated again on 20th-Century Dreams in 1999, with illustrations of political and world historical figures.He died at the age of 74 of cancer.