He took part in several explorations in the northwest and west coast of Africa which were made by Prince Henry.

In his second year, he took park in an expedition in the island of Arguin (now in Mauritania) with Antão Gonçalves and Garcia Homem.

His ship passed by a frontier coast of the island, discovered its cape, in that region had a large number of captives, which were returned to Lisbon, where they were sold.

On a royal map of Alphonso V dated 29 September 1462, the king brought it for Infante Don Fernando, his brother, of an island "Northwest of the Canary Islands and Madeira", it said: (...) asi e pela guisa que lhe temos dada a outras sete ilhas que Diego Affomsso seu escudeiro achou através do Cabo Verde Secondly on the same map, Diogo Afonso discovered five islands more west in Cape Verde including Brava, São Nicolau, São Vicente and Santo Antão and the islets of Branco and Razo.

[1] Diogo Afonso later settled in the island of Santiago and inhabited Ribeira Grande and was one of the first settlers of the island, there on 29 January 1462, he became the first of two captains of the island of Santiago which was governed in the then colonial capital of Ribeira Grande, he remained captain until 1473, from 19 September 1462, as captain of Southern Santiago which he was succeeded by his brother or son Rodrigo Afonso.