After some appearances in Tout le Western and Bunny, he began an association with the magazine Pif Gadget and Éditions Vaillant in 1970. He teamed up with writer Jean Ollivier and created his most famous series, 'Docteur Justice'. In the same magazine, he additionally illustrated 'Amicalement Vôtre' (Victor Mora's adaptation of the British TV series 'The Persuaders'), 'Taranis' (texts by Ollivier and later Mora), 'Tarao' (text by Roger Lécureux) and 'La Guerre du Feu'.
From 1973 to 1976, Marcello illustrated 'John Parade, Patrouilleur de l'Espace' with text by Maric in Le Journal des Pieds Nickelés. He contributed to the Larousse series 'L'Histoire de France en Bandes Dessinées', 'La Découverte du Monde' and 'L'Histoire du Far West' from 1976 to 1985. He was present in Le Journal de Mickey with 'Le Regard du Tigre', 'Zorro' and 'Le Club des Cinq'. Together with Maric, he produced the science fiction series 'Cristal', as well as the collection of short stories called 'Voulez-vous de Nos Nouvelles?', in Spirou from 1981 to 1988.
He drew a comic about Michael Jackson for Hachette in 1988, and the series 'Wayne Thunder', written by Alain De Kuyssche, for Le Lombard.