Héctor D’Adderio was born in Buenos Aires, Argentina on April 2, 1931. After starting his career in Argentina he played in Mexico, El Salvador and Canada.
Form 1954 until 1956 Héctor played for Atlas in Mexico. In the 1956-57 season he was with Mexican club Oro. He moved to El Salvador for the 1957-58 season, helping his club CD FAS in San Salvador winning the league championship that season. In May 1959 he played with CD FAS in the Campeonato Centroamericano.
In July 1959 Hector joined Montreal Canadian Alouettes in the National Soccer League. The inside forward was 5 feet 11 inches in height. The Canadian Alouettes had a dissapointing mid-table finish in the 1959 National Soccer League season.
On September 20, 1959 Hector scored one of the goals to help Canadian Alouettes defeat Westminster Royals 3-2 in the Canadian Championship final. The game was watched by a crowd of 3,000 at Fred Hamilton Park in Toronto.
Hector returned to Montreal in May 1960. The Canadian Alouettes had by now changed their name to Montreal Concordia. The club finished third in the 1960 National Soccer League regular season. Hector scored 13 league goals in the 1960 season.
Hector returned to Montreal in April 1961 from San Salvador. On April 6, 1961 the Montreal Gazette rated him as one of the best inside forwards to have been seen in Montreal. The club ended the 1961 National Soccer League season in second place, five points behind Toronto Roma.
The club also competed in the International Soccer League and the Canadian Challenge Cup. Concordia won the 1961 Canadian Challenge Trophy by beating Vancouver Firefighters 1-0 on July 29, 1961 in Montreal.