Ernesto Rudesindo García Seijas was born in Ramos Mejía, Buenos Aires, and began drawing comics at the age of seventeen. His early work appeared in Totem and starting in 1958, he illustrated the title comic of the magazine Bucaneros. He contributed to most of the Argentine comics magazines of the time, such as Frontera, Hora Cero ('Tom de la Pradera' with Oesterheld), Misterix ('León Loco' with Oesterheld, 1963), and Rayo Rojo. He illustrated some episodes of the 'Robin Hood' book collection of Acme publishers, and he also made comic adaptations of movies and some one shot comics for Intervalo, a female magazine of Editorial Columba. He worked with Robin Wood on 'Helena'.
He began a collaboration with Editorial Record and created several series with scriptwriters like Ray Collins, Carlos Trillo, Alfredo Grassi, Carlos Albiac and Andrea Mantelli, including 'Black Soldier', 'Skorpio', 'Mandy Riley', 'El Pequeño Rey', 'La Estirpe de Josh', 'Los Aventureros' and 'El Hombre de Richmond'. He also worked for Editorial Columba, where he created 'Kevin' with Robin Wood for Nippur magazine. For the daily Clarin, he made 'El Negro Blanco' and 'Flopi' with Carlos Trillo in 1987. Garcia Seijas' work has also been published in Spain and Italy.
For the Italian market, he made among others 'Radzel' with Eduardo Mazzitelli (Editorial Eura, 1999) and stories with 'Tex' (Bonelli). In the 1990s, he also took on stories in the terror genre for the magazine Espectator fo Editorial Perfil, and made stories with 'Bardo' for the daily La Prensa. He also appeared on the pages of La Nación with 'Especies en Peligro' in 2000.