Hart conducted her regular shakedown cruise off California and during her training participated in experimental high-speed refueling exercises with Kaskaskia.

She arrived off Brunei Bay on 9 June 1945 and commenced a patrol of the South China Sea to guard against possible interference from the remains of the Japanese Fleet at Singapore.

During the period of 19–21 June, she provided close support for further landings on the coast of Borneo near Brunei Bay, and then departed for Balikpapan and other amphibious operations.

While there, Hart patrolled, provided star shell illumination, and directed minesweeping vessels through the treacherous enemy minefields off the beaches.

She next moved to Subic Bay for training exercises and escort duty, and after the surrender of Japan on 15 August was assigned to the newly formed North China Force.

This duty completed, Hart sailed for China, escorting Cruiser Division 6 in an important show of force off the coast.