From 1464, Duarte was a secretary and notary to the crown under kings Afonso V, John II and Manuel I, who entrusted him with many embassies.
This he justified by appeal to the millenarian teachings of Joachim of Fiore and the objectives of recovering Jerusalem and blockading of the Red Sea.
An undated letter by Duarte to Afonso de Albuquerque develops his religious conception of the Portuguese expeditions.
They had one daughter, Isabel de Albuquerque Galvão, who on 25 April 1504 married Jorge Garcês, secretary of Manuel I.
With her, he had three daughters (Isabel, Leonor and Violante, who married Pedro Anes do Canto) and seven sons (Guiomar, Simão, António, Jorge, Manuel, Francisco and Rui).