After further training at Pearl Harbor, Hawaii, Mingo departed on her maiden war patrol on 25 June 1943.

She made damaging attacks on three Japanese merchant ships and bombarded Sorol Island off the Palaus before returning to Pearl Harbor for refit.

Although her primary operation was lifeguard duty in support of the US Thirteenth Air Force strikes on the Philippines and Borneo, she sank four coastal freighters.

Mingo did a noteworthy job as lifeguard as she rescued 16 B-24 Liberator fliers shot down off Balikpapan, Borneo; six of them from rubber boats in Makassar Strait and the other 10 from the beach of Celebes Island.

On 4 October, a U.S. Navy PB4Y-1 Liberator patrol bomber mistakenly attacked her, dropping a 100-pound (45 kg) bomb which landed 100 yards (91 m) from Mingo, inflicting no damage or casualties.

On 25 November, Mingo made a night torpedo attack on a Japanese convoy on a run between Singapore and Brunei, Borneo.

[8] The sinking of a maru of that name was prophetic, for the Japanese were only three months away from losing their hold completely on the ship's namesake, the Philippine capital.

Mingo was transferred on loan to Japan under the Military Assistance Program and renamed Kuroshio (SS-501) on 15 August.