She participated in the War of the Pacific, with her most prominent action being her victory over the Peruvian turret ram Huáscar in the Angamos naval battle.

The ship was named after Thomas Cochrane, a British naval officer who served as the first Vice Admiral of Chile, leading the Chilean Navy during the War of Independence.

In 1871 the president of Chile, Federico Errázuriz Zañartu, initiated a bill in the Chilean congress to authorize the executive to purchase two armored vessels.

The bill passed with only one opposing vote (that of the former president José Joaquín Pérez Mascayano), and provided for two medium-sized ships and that the total cost of the purchase would be 2,000,000 pesos.

In January 1878, once the dispute with Argentina had been settled, President Aníbal Pinto instructed Alberto Blest Gana to arrange for the sale of the two central battery ships in order to alleviate the economic crisis that had prevailed in Chile for several years.

On behalf of Blest Gana, E. J. Reed offered Almirante Cochrane to the UK for the sum of 220,000 pounds sterling, but the British declined.

Almirante Cochrane was 64.0 m long, with a beam of 14.0 m and a draft of 6.0 m. The hull had a maximum displacement of 3650 t when fully loaded with fuel, fresh water, weapons, ammunition, food and crew.

Supplementing this was a 20-pounder cannon, and one 9 and one 7 pounders, and a Nordenfeldt machine gun installed in the COFA's ratchet, one-inch-caliber (25.4 mm), which fired a one-pound (454 grams) projectile.

The power plant, provided by the company John Penn & sons, consisted of two compound steam engines, six boilers and two propellers.

Almirante Cochrane participated in the War of the Pacific, most prominently taking part in the defeat and capture of Peruvian monitor Huáscar in the Naval Battle of Angamos, on 8 October 1879.

At the start of the war Almirante Cochrane was commanded by Captain Enrique Baeza Simpson and since 5 April was present at the blockade of Iquique.

At the end of June 1879 Almirante Cochrane was the flagship of the 2nd Naval Division, in charge of the blockade of Iquique with the gunboat Magellan, the corvette Abtao and Matias Cousiño.