The ship was operated by the Lighthouse Service of the Commerce Department. On 11 April 1917, she was transferred to the Navy with the entire Lighthouse Service by executive order. Assigned to the 3rd Naval District, Mistletoe served during World War I as a patrol boat out of Section Base No. 8, Tompkinsville, Staten Island. Following the end of the war, the vessel was returned to the custody of the Department of Commerce, 1 July 1919.