Holguín was born around 1486 in a Spanish town called Tona or Sona. He arrived in the Americas very young and settled in the Spanish colony in present day Dominican Republic in 1506. There he participated in the foundation of the cities of Aragua, Puerto Real and Ciudad de la Vega. Captain Diego de Holguín participated in the conquest of Guatemala, Izalco, Cuscatlan and under the command of Pedro de Alvarado. He was alderman of the municipality of Santiago de los Caballeros de Guatemala. Along with Gonzalo de Alvarado, was one of the founders of the first settlement of San Salvador, next to a fortress Cuzcatlecos, and became its first mayor in April 1525.