He was the "grandson of a lyrical singer, in a family that had produced generations of musicians",[1] and the son of Jean-Claude Beïret Montagné, a radio and electronics engineer who during the Vichy years went underground rather than submit to forced labor conscription; was imprisoned in Pamplona under the Franco regime; but eventually joined the Free French in Casablanca.

[2] In 1972, he graduated from René Simon's acting school and quickly found employment in the films of Robert Manuel as well as Luis Buñuel, who cast him as the Young Monk in The Phantom of Liberty (1974).

In 1978, Stéphane Collaro engaged him to perform imitations and write comic texts of his radio program on Europe 1.

The Collaro troop pass from Antenne 2 to TF1 and the show was retitled Co-Co Boy where Guy Montagné met American coco-girl Terry Shane.

In February 2014, he was victim of a facial nerve paralysis on the left side called Bell's palsy, due to the stress of the ticket theft of the show he had to play in the town of Muzillac in the department of Morbihan,[3] and the way he was treated by the municipality after the theft, who refused to reimburse him.