Born in Spain, Aragones emigrated with his family due to the Spanish Civil War, and settled in Mexico. He made his first professional sale in 1954 and has continued to doodle humorous cartoons throughout his tenure studying architecture. Aragones was a long-time contributor to Mad Magazine. He was famous for his wordless "drawn-out dramas" appearing in the margins and between panels of the magazine, both horizontally and vertically as well as occasionally around corners.
In 1967 he began illustrating full stories for DC Comics on such titles as Plop and Bat Lash.
In the 1980s he created the humorous barbarian book Groo the Wanderer (so named because he sought a name which meant nothing in any language) with Mark Evanier. As a creator-owned book, Groo has survived the bankruptcy of a number of publishers. The book was initially published by Pacific Comics, then Marvel Comics under their Epic imprint, then Image Comics and currently Dark Horse Comics.