After Tamandaré was repaired she provided fire support for the army for the rest of the war, aside from bombarding Paraguayan capital of Asunción once.

Tamandaré was designed to meet the need of the Brazilian Navy for a small, simple, shallow-draft armored ship capable of withstanding heavy fire.

She was one of three armored gunboats, together with Barroso and Rio de Janeiro, built to the same general plan, although each ship varied significantly in size and armament.

[1] Tamandaré had a single John Penn & Sons 2-cylinder steam engine taken from the British-built wooden gunboat Tietê and proved unreliable in service.

The engine, which drove a single 2-bladed propeller, was powered by two tubular boilers that produced a total of 273 indicated horsepower (204 kW) which gave the ship a maximum speed of 8 knots (15 km/h; 9.2 mph).

The ship arrived at Corrientes on 16 March 1866; the next day she sailed for the confluence of the Paraná and Paraguay Rivers to begin operations against the Paraguayans.

During her bombardment on the following day, a shell entered one of her gun ports, despite the chain curtain that protected it, and killed 14 men, including her captain, lieutenant Antônio Carlos de Mariz e Barros, and wounded 20.

The ship bombarded Curuzú Fort, downstream of Curupaity, on 1 September in company with the ironclads Rio de Janeiro, Brasil, Lima Barros, Barroso, and the monitor Bahia.

[6] They were quickly repaired and Tamandaré bombarded Paraguayan artillery batteries at Timbó that commanded the Paraguay River north of Humaitá the next day.

On 26 September the Paraguayans moved a large-caliber gun below Humaitá and bombarded the Brazilian squadron, but it was silenced by gunfire from Tamandaré and Bahia.

Three Pará-class river monitors, Rio Grande, Alagoas and Pará, were lashed to the larger ironclads in case any engines were disabled by the Paraguayan guns.