After being fitted out for overseas service, Harvard departed New York City 9 June 1917 with a convoy, and arrived at Brest, France, 4 July.

She then engaged in patrol duties out of Brest, and on 16 July picked up 59 survivors from the ill-fated British steamship Trelissick.

Continuing her duties around Brest, Harvard performed as a harbor patrol and coastal convoy ship.

She assisted the torpedoed merchantman Texas 29 November 1917 and searched for survivors of the sinking of Hundaago, a Norwegian steamship, 4 August 1918.

Harvard departed for England 21 November 1918 and remained there until June 1919, when she returned to New York City via Bermuda.