[1] During World War II she served in the following actions: At the inconclusive First Battle of Sirte, which came about as a British attempt to intercept the resupply of Benghazi, Attendolo was part of the "Close covering force" for Convoy M42.

Passing through the patrol area of two British submarines, Muzio Attendolo was torpedoed by HMS Unbroken in the early morning of 13 August.

She lost all the hull forward the first turret, but the transversal bulkhead resisted enough to save her from flooding, and the loss of the damaged part lightened the ship herself.

All this could have been effective with classical naval warfare, but airpower soon changed things drastically, as shown in the Battle of Taranto and Naples port attacks (1940–41).

On 4 December 1942 (St. Barbara's Day), 20 USAAF B-24s of 98th and 376th Bombardment Groups, based in Egypt and armed with 500 and 1000 lb bombs from 6,200 m (20,300 ft), flew to Naples unnoticed.

Muzio Attendolo was hit in the midship by one or possibly two bombs, between tower 3 and part of her superstructure, cutting off her main power, and effectively taking her out of the fight.

The fires had finally been extinguished when another air-raid alarm was sounded at 21:17, sending repair crews and craft scrambling for cover from the anticipated 2nd wave air-attacks.

The impending 2nd air-attack would prove to be a false alarm, and the repair personnel and vessels attending Muzio Attendolo would not return to her aid until over an hour later.

The ship was used as a dock with the Allied occupation; after the war's end, given that the structures of the ship were still in a good condition, it was considered the possibility of salvaging it and transforming it into an anti-aircraft cruiser (to be included in the Navy in the place of the old cruiser Luigi Cadorna), but the lack of financial means and the fear that the Allied Commission would oppose the proposal, led to Muzio Attendolo being raised and scrapped instead.