Brollo was ordained to the priesthood in 1957. He was titular bishop of "Zuglio" and auxiliary bishop of the Roman Catholic Archdiocese of Udine, Italy, from 1985 to 1995. He then was bishop of the Roman Catholic Diocese of Belluno-Feltre, Italy, from 1995 to 2000. Brollo was archbishop of the Udine Archdiocese from 2000 to 2009.