Commissioned into service in the Italian Regia Marina (Royal Navy) in 1913, she served in World War I, playing an active role in the Adriatic campaign and seeing action in the Battle of the Strait of Otranto.

The squadron, under the command of Capitano de fregata (Frigate Captain) P. Orsini, was based at Taranto, although either Impetuoso or Indomito or both were visiting La Spezia that day.

[2] A few hours after an Austro-Hungarian Navy force subjected the Palagruža (known to the Italians as the Pelagosa) archipelago in the Adriatic Sea to a heavy bombardment during the night of 16–17 August 1915, Impavido, Intrepido, the protected cruiser Quarto, and the destroyers Animoso and Ardito, which were on a cruise in the Adriatic Sea north of the line Brindisi–Cattaro, interrupted their operations to respond.

[2] At 19:00 on 8 June 1916 Impavido, under the command of an officer named Ruggiero, departed Vlorë (known to the Italians as Valona) in the Principality of Albania with Insidioso, the protected cruiser Libia, and the destroyers Espero and Pontiere to escort the armed merchant cruiser Principe Umberto and the troopship Romagna, which had embarked the 2,605 men of the Italian Royal Army′s (Regio Esercito′s) 55th Infantry Regiment for transportation to Italy.

Principe Umberto sank in a few minutes about 15 nautical miles (28 km; 17 mi) southwest of the Karaburun Peninsula (also known as Cape Linguetta) with the loss of 1,926 of the 2,821 men on board, the worst naval disaster of World War I in terms of lives lost.

[2] On 24 December 1916 Impavido, the scout cruiser Carlo Mirabello, and the destroyer Ippolito Nievo supported an operation by the motor torpedo boats MAS 3 and MAS 6, which, towed respectively by the coastal torpedo boats 36 PN and 54 AS, were supposed to attack Austro-Hungarian ships in port at Durrës.

The Italians aborted the attack when MAS 6 suffered damage in a collision with wreckage 3 nautical miles (5.6 km; 3.5 mi) from Durrës.