Sagittario was built in the late inter-war period by Cantieri Navali Quarnero (CNQ), Fiume, one of the Perseo sub-group of the Spica class.

[3] On 10 June 1940, when Italy declared war against the Allies, Sagittario was part of the 10th Torpedo Boat Flotilla based on La Spezia.

News of this setback caused the recall of the 2nd Motor Sailing Flotilla, but these orders did not reach it until 09:30 on the 22nd, when the small vessels were approximately 25 miles (40 km) off Milos.

King decided to engage, but Sagittario laid a smoke screen, launched torpedoes and exchanged fire with the British force,[10][9] trying to lure them away from the convoy position.

King's warships, despite their failure to destroy the German troop transports, had succeeded in forcing the Axis to abort the landing by their mere presence at sea.

King, knowing that his ships were low on anti-aircraft ammunition and feeling that he had achieved his main objective, ordered Force C to withdraw.

[20] On 19 October, Sagittario rescued the survivors of the Italian destroyer Giovanni da Verrazzano, torpedoed and sunk by the British submarine Unbending.

The convoy was targeted by Fairey Albacores bombers from Malta on 2 December, and the motor vessel Veloce was hit by a torpedo and left in a sinking condition.

Sagittario's sister Lupo was sunk by British Force K while rescuing survivors, while Chisone, the other merchant of the convoy, reached Tripoli the following day along with her escorts.

[23] On 8 September, the day of the Cassibile Armistice, Sagittario was at Pola, from where she escorted the battleship Giulio Cesare to Taranto to meet Allied forces.