Catskill sailed from San Diego on 12 August 1944 for Hawaii, where she embarked marines, and proceeded by way of Eniwetok for Manus, where she joined the transport group of the Southern Attack Force for the assault on Leyte.

Catskill returned to New Guinea and then sailed to Morotai, where from 5 to 10 November 1944 she loaded troops and cargo under almost continuous enemy air raids.

As her convoy proceeded north with these reinforcements for Leyte, it came under enemy air attack on 13 November, and Catskill's gunners contributed to shooting down Japanese aircraft.

She arrived in San Francisco 27 October, and sailed again 10 November on the first of two more voyages to bring troops home from Guam, Ulithi, Peleliu, and Eniwetok.

On 21 December 1945 Catskill sailed from San Diego for Guam with the 90th Marine Corps Replacement Draft which was eventually headed for China.

Laid up in the Pacific Reserve Fleet, San Diego Group, Catskill was reclassified under SCB 123 as mine countermeasures support ship MCS-1 on 18 October 1956.

Converted to an MCS in fiscal year 1964 at Boland Machine Manufacturing Company of New Orleans, Louisiana from 25 June 1964 to 8 September 1967, Catskill (MCS-1) was recommissioned 6 October 1967.