Emilio was born as the son of Colombian captain and veteran of the Spanish American Wars of Independence Pío Díaz and María Luisa Seminario who was a part of an influential family within the Department of Piura.

In 1850, he would be assigned to the brigantine Guise and in the following year, would serve aboard the French corvette Serieuse, sailing to Oceania and later Europe.

Later, he was made in charge of the steamer Izcuchaca during the Peruvian Civil War of 1856–1858 as he would remain loyal to the government of Ramón Castilla, in contrast to other naval figures such as Miguel Grau and Lizardo Montero who would side with the rebels.

[3] Then promoted to naval Captain, he would participate in the Spanish-South American War within the Battle of Callao on 2 May 1866, stationed at the Real Felipe Fortress under the orders of Ignacio Mariátegui y Tellería.

He would be survived by his son also named Emilio Díaz who was also a naval veteran of the War of the Pacific, serving aboard the BAP Unión.