After taking part in the war between Spain and France, he travelled to America in 1945. He was at the service of Pedro de La Gasca and stayed in Perú until he travelled to Chile in 1552. He participated with Pedro de Valdivia in several campaigns in Chile, filling several military offices as a captain. He also participated in the campaigns of governors Hurtado de Mendoza and Rodrigo de Quiroga.
Between 1575 and 1576 he wrote Crónica del Reino de Chile, where he narrated all the events in which he participated during the Chilean conquest. The jesuit Bartolomé Escobar wrote this work again with the title Crónica del Reino de Chile que escribió el capitán D. Pedro Mariño de Lobera, arreglada y reducida a nuevo método y estilo por el P. Bartolomé Escobar, de la Compañía de Jesús.