Merganser was laid down as YMS-417 by Stadium Yacht Basin of Cleveland, Ohio on 9 January 1944; launched 29 June 1944; and commissioned 11 November 1944. Assigned to the 1st Naval District after commissioning, YMS-417 operated along the northern New England coast until 20 July 1945. She then got underway for Pearl Harbor and duty with the Pacific Fleet. Arriving in Hawaiian waters in October, she was assigned to the Philippine Sea Frontier and continued her voyage, reporting to ComPhilSeaFron in January 1946. The next month she was transferred to Minesweeping Squadron, Pacific Fleet.