On 12 May 1918 she was in a convoy on a crossing from New York City to Plymouth, England, when the U.S. Navy cargo ship USS Zaanland (ID-2746) suffered a rudder casualty that evening, went off course, and was rammed by the U.S. Navy tanker USS Hisko (ID-1953).

Assigned to the Naval Overseas Transportation Service (NOTS), Munalbro joined a convoy at New York City bound for Europe on 26 September 1918.

She arrived at La Pallice, France, on 13 October 1918 to discharge part of her U.S. Army general cargo and continued on to St. Nazaire, Nantes, and Quiberon.

On 12 December 1918 Munalbro made a second crossing to Quiberon, where she arrived in January 1919, again carrying general U.S. Army supplies.

On 21 March 1919 Munalbro decommissioned and was delivered to the United States Shipping Board for simultaneous return to Munson Steamship Line.