Following commissioning, Seer proceeded from the Great Lakes to Chesapeake Bay for shakedown; then commenced minesweeping, anti-submarine patrol, and coastal escort work in the 5th Naval District.

Eight of her crew were injured; but, by the 19th, she was back at Palermo, whence she proceeded to Licata, Bizerte, and then to Mers El Kébir to prepare for the invasion of the Italian mainland at Salerno.

Seer continued to escort merchant ship and amphibious convoys to Italy into the summer of 1944 when she joined the forces assigned to Operation "Dragoon," the landings in southern France.

Departing Naples on 12 August, she moved toward the French coast; and, during the pre-dawn hours of the 15th, commenced sweeping the boat lanes leading to "Red Beach" on the Baie de Cavalaire.

Further sweeping operations in the assault area and off Toulon and Marseille followed; and, for almost a month, she escaped damage from German mines and coastal guns.

Sailing via Bizerte and Oran, Seer arrived at Yorktown, Virginia, on 11 December and began repairs at the Norfolk Navy Yard on the 14th.

In early May, she transited the Panama Canal en route to Pearl Harbor where she rejoined her division, now assigned to the Pacific Fleet.

She arrived at San Pedro on 14 February; remained on the west coast into November; then got underway for Orange, Texas, where she was decommissioned on 26 April 1947 and berthed with the Atlantic Reserve Fleet.

Recommissioned on 8 November 1950, she joined MinDiv 8 and for the remainder of the war performed training and schoolship duties out of Charleston, South Carolina, conducting periodic tours at Mayport and Panama City, Florida.