When America was preparing to enter World War I, Berry again enlisted as a private in the 14th Infantry. He was commissioned a major of infantry, transferred to the 106th Infantry, 27th Division, and set sail for France in May 1918. He commanded the 2nd Battalion of the 106th, stationed in the Ypres sector in Belgium. He was then promoted to lieutenant-colonel and transferred to the 105th Infantry. He led the regiment at Dickebusch Lake and the Battle of Vierstraat Ridge. He was second in command of the regiment in the Battle of the Hindenburg Line and the subsequent advance to Canal De La Sambre. After the Armistice was signed, he returned to the United States in November 1918. For his military service, he was awarded the Croix de guerre with Palms, the Conspicuous Service Cross, and was cited for gallantry in action.