He studied at the Instituto Nacional and later graduated as a lawyer from the Universidad de Chile.
He was accepted to the bar on May 18, 1869. He was elected Deputy for Lontué in 1885 and reelected in 1891. In 1894 he was elected for the Talca, Curepto and Lontué district.
Fernández was twice Minister of Industry and Public Works under President Jorge Montt (1894-1896).
Minister of War and Navy (1896-1897), Finance (1897) and Interior (1899-1900) under Federico Errázuriz Echaurren, and again minister of Interior under Germán Riesco (1902-1903). In 1910, President Pedro Montt, seriously ill, took a leave of absence and moved to Germany for treatment, which proved unsuccessful, and Fernández, as Minister of the Interior, served during Montt"s absence and became acting President upon Montt"s death on August 16, 1910.
Fernández, however, caught a cold during Montt"s funeral, which soon turned into pulmonary, causing him to die of heart failure in Santiago de Chile on September 6, 1910, after only three weeks in office.