Ellis's first cruise, between 16 June and 15 August 1919, was to the Black Sea, carrying United States Food Administration officials for famine relief work, and British and American military officers between Constantinople, Turkey; Varna, Bulgaria; and Batum, Georgia.

Based on New York through the summer of 1933, she escorted the Presidential yacht along the New England coast to Campobello, New Brunswick, where on 1 July she embarked President Franklin D. Roosevelt and his party, transferring them to the cruiser Indianapolis.

The next year, Ellis cruised to Cuba, again escorted the president, this time in a private yacht, and on 24 October 1934 passed through the Panama Canal to be based on San Diego.

Between 20 March 1943 and 25 June, Ellis escorted two top priority tanker convoys with Aruba oil for North Africa, then troop transports to Derry.

Returning to North African convoy duty, Ellis made two voyages from the east coast to Casablanca, Algiers, and Bizerte between February and June.

The remainder of the war, Ellis guarded carriers training pilots, experimented with torpedo aircraft, twice made escort voyages to Recife, Brazil.