In mid-1911, Elliott was ordered to , transferring to . While on "Florida", he participated as a Surgeon in the intervention at Vera Cruz, Mexico. On April 21, 1914, he quickly established a base hospital and supervised the removal of the wounded and field station operations until the city's capture the next day. For his "distinguished conduct in battle" on this occasion, he was awarded the Medal of Honor. That summer, he reported for shore duty at the Navy Recruiting Station in New York City. While on recruiting duty in August 1916, he was promoted to Medical Inspector with the corresponding rank of commander. During World War I, he commanded the Naval Hospital and Supply Depot at Cañacao Bay, Philippines. In January 1918, Elliott was promoted Medical Director with the corresponding rank of captain. Returning to Washington D.C. in December 1919, he assumed command of the Naval Hospital.