Cowell was launched 18 March 1943 by Bethlehem Steel Co., San Pedro, California, sponsored by Mrs. R. Hepburn; and commissioned 23 August 1943.

After an overhaul at Eniwetok, Cowell put to sea 29 August 1944 with Task Group 36.5 (TG 38.5) for air strikes on the western Carolines, the Philippines and the Palaus, and the Manila and Subic Bay area, as well as to support the landings on Morotai on 15 September.

She arrived at Manus on 28 September to replenish, then sortied 2 October supporting air strikes on Okinawa, Luzon, and Formosa preparing for the Leyte assault.

When Canberra and Houston were torpedoed in heavy Japanese air attacks on 13 and 14 October, Cowell stood by to furnish light, power, and pumping facilities as the cripples slowly retired from the danger area.

She rejoined her task force to sail for the far-flung Battle for Leyte Gulf, and aircraft from her carriers were in time to launch telling strikes against the retreating Japanese ships.

Until 20 June Cowell braved the hazards of the picket line to direct combat air patrol successfully and to shoot down her own share of Japanese aircraft with antiaircraft fire.

On 4 May she shot down two planes within 50 feet of the ship, receiving a shower of gasoline and burning debris, then aided Gwin by firing on another kamikaze.

She cleared Sasebo 26 June to complete her cruise around the world calling at Manila, and passing through the Indian Ocean, the Suez Canal and the Mediterranean Sea to return to Norfolk 22 August.