Walter Fahrer studied Fine Arts in Buenos Aires before making his professional debut in 1957. He did several cover illustrations for publisher Lainez before he created his first comic, 'Tee Howard', for the same publisher. Afterwards, he illustrated several stories with 'Ernie Pike', with scenarios by Oesterheld, in Hora Cero. In 1959 he was one of the co-founders of the magazine Fuego, where he also started to write his own scenarios again. For the publisher Abril, he drew 'Nat Mandell' in Misterix and Rayo Rojo, and for Divito, he did many short stories.
In the early 1960s he moved to Europe, where started a cooperation with Universo in Milan and eventually the Frech Opera Mundi. Until the mid-1970s, he illustrated numerous daily comics through this agency, including 'Le Roi de Paris', 'Au Fond du Gouffre', 'Les Dames de Croix-Mort', 'La Dame de l'Ouest', 'Lunegarde', 'Les Indes Noires', 'Le Pays d'Où on ne Revient Jamais', 'La Belle de Port-au-Prince', 'Mandrin', 'Lady Stanhope', 'Fournier Sarlovèze', 'Aleonor d'Aquitaine', 'Bataille de Femmes', 'OSS 117', 'AVentures Exotiques' and 'Janique Aimée'.
After a while, Fahrer travelled to the USA and back to Argentina, where he drew several series for Columbo. In late 1968 he started working for Tintin magazine, starting with several historical comics. He eventually created the 'Cobalt' series with scripts by Greg. In 1973 he returned to Argentina for good, and launched the 'Gato Montes' western series. With the French scenarist Claude Moliterni, he started the series 'Harry Chase', a police saga published in France-Soir, Télé 7 Jours and Charlie Mensuel. In the 1980s, Fahrer worked for the magazines Vécu ('Le Casque et la Fronde' with François Corteggiani) and Pilote ('Captain Hard'). In 2000, he made 'Mon Nom n'est pas Wilson' with Carlos Trillo at Casterman.