Gallieno Ferri was born in Genoa. He studied geometry before working on comic strips. He began his career using the pseudonym Fergal, and cooperating with the publisher and scriptwriter Giovanni De Leo. Together, they realised 'Il Fantasma Verde' and 'Piuma Rossa'. From 1949, he drew the first episodes of 'Maskar', the western 'Tom Tom' and created 'Thunder Jack', a series inspired by Zane Grey's 'King of the Royal Mounted'. He also produced artwork for the French market, including 'Kid Colorado', 'Jim Puma', 'Agent Secret', 'Le Fantôme Vert', all published by the Éditions SER.
In the late 50's he worked for Il Vittorioso, where he drew the adventures of 'Capitan Walter' (script by Sandro Cavore), 'Jolly' and 'Ali Baba'. In 1961, Ferri began his cooperation with Bonelli, starting with the Canadian Mountie story 'Giubba Rossa'. He eventually created the adventures of 'Zagor', for which he drew many episodes and all of the series' covers. In 1975 he drew the first story of 'Mister No'. Later on the strip was continued by Roberto Diso and other artists. In addition, Ferri drew for the British Fleetway agency, contributing to 'Dick Daring of the Mounties'.