1944

From commissioning until mid-January 1944, Swearer was attached to the Operational Training Command, Atlantic Fleet for shakedown training and post-shakedown availability. On 19 January 1944, she put to sea from New York City in the screen of a convoy of troop transports bound for the Panama Canal. She transited the canal at the end of January and continued on to Hawaii. Swearer arrived in Pearl Harbor on 15 February and remained there until the 29th, conducting training and undergoing repairs. On the 29th, she set sail for Eniwetok Atoll in the screen of a convoy and, after a stop at Kwajalein, reached her destination on 8 March.

For a little more than ten months, Swearer contributed to America's war effort in the Pacific by shepherding the logistics groups which supported the fighting. During the bulk of the time, she operated from Eniwetok and Ulithi atolls, screening the fueling group of the 3rd/5th fleets to and from fueling rendezvous. In being so engaged, the destroyer escort participated in the raids on Palau, Yap, Woleai, Truk, Sata-wan, and Ponape in March and April 1944.

In early April, she also screened escort carriers from Manus to resupply rendezvous with the larger carriers then engaged in operations in western New Guinea. After a month at Pearl Harbor in repairs, she returned to the central Pacific and to screening duty with the fueling group. She participated in the capture and occupation of the Mariana Islands between June and August, then moved south to Manus to screen escort carriers during the western Carolines and Leyte operations. In November, Swearer resumed duty with the fueling group. During these last three months with the fueling groups, she supported the fast carriers as they struck Luzon in the Philippines and as they made their sweep of Formosa, the China coast, and of the Nansei Shoto.

1945

After repairs and upkeep at Ulithi in the western Carolines, from 21 January to 6 February 1945, Swearer joined a convoy of cargo and troopships bound for the invasion of Iwo Jima. The convoy stopped at Guam for a week, then headed for Iwo Jima on 6 February. Swearer and her convoy arrived off the island on 19 February, the date of the assault. For five days, she patrolled the transport area and helped fight off Japanese air attacks, before departing on the 23rd for Leyte Gulf in the Philippines.

The destroyer escort remained in San Pedro Bay until 19 March, preparing for the invasion of Okinawa. Between the 19–26 March, she screened a convoy of cargo, troop, and amphibious warfare ships to the Okinawa staging area at Kerama Retto. Swearer remained in the vicinity of Okinawa for three months, patrolling, screening, escorting, and fighting off kamikaze attacks. She was attacked by a "Zeke" on the day of the invasion, but her gunners brought him down before he could crash her. On 16 April, a "Val" tried to crash-dive Swearer, but again her gunners brought him down. The destroyer escort continued to patrol Kerama Retto until 5 July. She suffered two more air attacks during that time, one by a bomber on 13 May and another by a torpedo bomber on 27 June. In both cases, however, neither plane nor ship inflicted damage upon the other.

For the duration of the war the Swearer was under the command of Captains John M. Trent and Kenneth H. Hannan. During her long tour of duty the Swearer received a total of 9 battle stars, 7 for the Philippine liberation and 2 for surviving without injury or damage following actions of aerial strafing, aerial torpedo, dive-bombing, two kamikaze attacks, and Typhoon Cobra.

Swearer returned to Eniwetok on 12 July, and headed for the United States on the following day. After a stop at Pearl Harbor, she entered San Diego on 27 July, and commenced overhaul. Three months later, she headed south to the Panama Canal, transited it on 4 November, and headed north to Norfolk, where she arrived on 10 November.