Aaron Ward (DD-132) reported to the Atlantic Fleet upon commissioning. Her first duty was at Trepassy Bay Newfoundland, In May 1919 as station ship for the trans-Atlantic flight Of the NC-1, NC-3 , and NC-4 Reporting to the Pacific Fleet September 1919, she spent the following month salvaging a sunken Army airplane in Angeles Bay, Mexico. Her training and exercise with the Battle Fleet were interrupted, January-March 1921, by a search for the seaplane NC-6 , which had crashed off the Canal Zone; and the rescue of survivors from Woolsey (DD-77), rammed by a steamer 20 February 1921. During the ensuing years Aaron Ward's status changed several times.

She was out of commission from 17 June 1922 till 24 May 1930 and again from 1 April 1937 till 30 September 1939 at San Diego, while from June 1932 to December 1934 she was a unit of Rotating Destroyer Squadrons 21 and 20. The remaining time was spent in full commission, and included serving flagship, Destroyer Division's 5 and 4. Recommissioned for the final time 30 September 1939 Aaron Ward served as flagship, Destroyer Division 85, Pacific Fleet, until she arrived at Key West, 11 December to operate on Neutrality Patrol in the Gulf of Mexico and Caribbean.

Transferred to the British in the destroyer, land bases exchange, Aaron Ward was decommissioned at Halifax Nova Scotia, 9 September l940 and and transferred to Royal Navy being renamed HMS Castleton.