He was a descendant of Don Diego de Sarmiento, a knight commander of the Order of Alcántara and gentleman in waiting to the king.

However, his tenure was short lived and the crown named Sarmiento de Sotomayor on 30 July 1642 to replace him.

Salvatierra landed in Veracruz in early October 1642 and arrived in Mexico City on 23 November 1642, and took up his duties as viceroy.

The period between Salvatierra's 1642 arrival and Palafox's forced departure in 1649 from New Spain for a minor bishopric in Osma, Spain "inaugurated a period of severe political tension, marked by the development of a powerful alliance bent on destroying Palafox's [reform] programme in all its manifestations.

On 13 May 1648 he turned the government of New Spain over to the new viceroy, Marcos de Torres y Rueda, bishop of Yucatán.