He began working professionally in 1947, playing with Aimé Barelli, Django Reinhardt, Don Byas, Hubert Fol, James Moody, Benny Golson, Bernard Peiffer, Fats Sadi, Lucky Thompson, Kenny Clarke, Blossom Dearie, Martial Solal, Michel Legrand and André Hodeir.
Guérin played at the 1958 Newport Jazz Festival with a youth ensemble, and played in Les Double Six in 1959, later returning to this group. He replaced Clark Terry in Quincy Jones's Big Band in 1960. He worked on the soundtrack to the film Paris Blues in 1961 with Duke Ellington. He worked extensively as a vocalist for Michel Legrand.
Guérin has over 150 album credits to his name. He won the Prix Django Renhardt in 1959.