The first photograph of him to be published appeared on the front page of the Diário de Notícias, of Lisbon, when Gageiro was twelve years old.
Gageiro had a worldwide exposure of his work when he photographed the events related to the Munich massacre that took place at the Olympic Games of 1972.
[4] Gageiro has photographed all around the world, including Cuba, where the Fidel Castro government allowed him to work with few restrictions, and East Timor, where he travelled to document life in the immediate post-independence period.
Gageiro work is similar of the postwar French photographers Henri Cartier-Bresson, Robert Doisneau and Willy Ronis.
Jorge Pedro Sousa, in his thesis on the history of photojournalism in Portugal characterised Gageiro's photographic practice by the same "aesthetic-compositional quality, human value and dramatic form" that are also found in W. Eugene Smith and Henri Cartier-Bresson.