Humberto Mergulhão began his career connected to radio in Porto, through a contract with the SPN-SNI (National Secretariat of Propaganda, later changed to National Information Secretariat). His main function was to prepare and read press reviews in the small local stations (Emissores do Norte Reunidos). He was identified as being aligned with the political regime, he later worked in Lisbon in radio and in the press (O Século). In 1943, he joined Rádio Voz de Lisboa, of Lacombe Neves, but the experience did not last long. After that, he went to Angola to Rádio Clube de Benguela. He was a reporter, commentator of football and roller hockey and author of theatre plays. He was head of radio services at CITA (Angolan Information and Tourism Centre), under the control of the general government, later transformed into Emissora Oficial de Angola. Important Angolan radio personalities worked with Humberto Mergulhão, such as Sara Chaves, Alberto Afonso, Alice Cruz, Rui Romano, Natália Bispo (his wife), António Santos e Sousa and Cremilde de Figueiredo. Humberto Mergulhão left the position in 1964, due to illness.