Before joining the Atlantic Fleet Delphy tested submarine detection devices at New London, Connecticut, from 23 to 31 December 1918 and aided survivors from Northern Pacific, stranded off Fire Island, New York, on New Year's Day, 1919.

Returning to New York on 14 April with the Fleet, she sailed for Boston, Massachusetts, on the last day of the month for operations in preparation for the first transatlantic seaplane flight.

She joined Destroyer Squadrons, Pacific Fleet, at San Diego for torpedo practice and recovery until placed in reserve on 12 June.

Delphy lay at San Diego until 27 December when she sailed with the other ships of Reserve Destroyer Division for Bremerton, Washington, arriving on 4 January 1921 for an extended overhaul at Puget Sound Navy Yard.

On 25 June she got underway with Destroyer Division 31 for a cruise to Washington for summer maneuvers with the Battle Fleet on the return passage.