Sá travelled to the colony of Brazil on the orders of the Portuguese crown to wage war on the French colonists commanded by Nicolas Durand de Villegaignon.

[1] These French colonists had established themselves in 1555 at Guanabara Bay in Rio de Janeiro, in a settlement known as France Antarctique.

On March 1, he founded the city of São Sebastião do Rio de Janeiro near the Sugarloaf Mountain and established the basis of his military operations against the French and their Indigenous allies.

[1] After receiving reinforcements sent by sea by his uncle from Salvador, Sá commanded a definitive and successful attack on the fortification of Uruçú-mirim on 20 January 1567.

As the city of Rio de Janeiro grew, his remains were relocated to a new church of Saint Sebastian in the Castelo.