After the United States entered World War I on 6 April 1917, "Montana" initially was tasked with transporting men and materiel in the York River area, along with conducting training exercises. On 17 July, she was assigned to the Cruiser and Transport Force; she spent the majority of 1917 and 1918 escorting convoys from Hampton Roads, New York City, and Halifax, Nova Scotia to France. These operations included a troopship convoy of four transports—, , , and —carrying part of the American Expeditionary Forces on 6 August 1917. In early 1918, she was briefly used as a training ship for naval cadets from the United States Naval Academy in the Chesapeake Bay. A troopship convoy followed in June 1918 in company with the cruisers and and the destroyers and , protecting the Italian steamers , , and , the French , and American transports "Pocahontas" and "Susquehanna".