Gomes da Costa had a distinguished military career in the country's colonies, from 1893 to 1915, in India, Mozambique, Angola, and São Tomé, having served under the command of Mouzinho de Albuquerque.

After World War I, in which he rose to greater prominence in the command of the 1st Division of the Portuguese Expeditionary Corps, he became actively engaged in politics, in staunch opposition to the dominant Democratic Party.

Following the military coup, Gomes da Costa deposed moderate José Mendes Cabeçadas, who had received executive and presidential power from the removed Prime Minister António Maria da Silva and President Bernardino Machado, briefly holding the headship of government and of state in the summer of that year, until he was himself removed by another coup, to be replaced by Óscar Carmona.

That, and his reputation as a soldier, led to his choice by right-wing revolutionaries to lead the 28 May 1926 coup d'état in Braga that overthrew the Portuguese First Republic, after General Alves Roçadas, their original choice, had fallen fatally ill. After the success of the revolution he did not assume power at first, entrusting the posts of President of the Republic and President of the Council of Ministers (Prime Minister) to José Mendes Cabeçadas, the leader of the revolution in Lisbon.

On 15 May 1885 in Penamacor Gomes da Costa married Henriqueta Júlia de Mira Godinho (Lagos, Santa Maria, 1863–1936), by whom he had three children.