[1] Following shakedown off Bermuda, Monssen steamed north to Boston, Massachusetts, to join the new cruisers Vincennes, Houston, and Miami and escort them to San Diego.

Included in her accomplishments during that period was her assistance in the breaking up of a large-scale enemy tank and troop counterattack, south of Garapan, at dawn on the 16th.

On the 20th, American aircraft staged a long range attack on the Japanese fleet and that night Monssen's searchlights were turned on to aid the planes back to their ships and locate and rescue downed crews.

[1] At dawn, Monssen resumed her patrol station and the next day departed for Hollandia, whence she screened reinforcement convoys to Leyte during November.

By 21 December, she was at Manus, whence she departed on the 30th to rendezvous with Task Unit 77.9.12 (TU 77.9.12) (landing craft of the reinforcement echelon) and proceeded to the northern Philippines.

[1] On 13 January, Monssen departed Luzon, escorted empty transports to Leyte, and then proceeded on to Ulithi, where she joined TG 58.5, the fast carrier night group.

Monssen remained in the Volcanos, screening the carriers and providing gunfire support for the land forces, until 9 March, when she returned to Ulithi.

For the next 7 weeks she served on radar picket stations and as plane guard as air operations were conducted in support of the Okinawa campaign.

[1] Rearmed at sea, the force returned to Tokyo on 9 August and on the 10th, Monssen and the other ships of DesRon 54, were detached with orders to proceed to the west coast for overhaul.

Heading north, the squadron joined TF 92 for an antishipping sweep of the northern Kuriles and the bombardment of Paramushiro, 11th, and then continued on to Adak, Alaska.

[1] At Adak, on the 14th, Monssen received word of the Japanese surrender, and new orders to return to Japan with TF 92 for occupation duty in the Ominato Naval Base area.

Transiting the Panama Canal, she arrived in the western Pacific 7 June and for the next 4 months patrolled off Korea and in the Taiwan Straits and conducted exercises in Japanese and Okinawan waters.

According to the Dictionary of American Naval Fighting Ships, in September 1957, she again decommissioned; this time berthing at Boston as a unit of the Atlantic Reserve Fleet.

[2] Transferred to the Philadelphia Reserve Group in 1962, Monssen was being towed down the coast when the towline parted in heavy seas due to the Ash Wednesday Storm of 1962.

With seas running 10 to 15 feet and wind gusting to 50 knots, she went aground on 6 March at Beach Haven Inlet, New Jersey, remaining there for 6 weeks before being pulled off and completing her journey.