When the Spanish–American War broke out, McCarthy tried to enlist, but was turned down for physical reasons. Despite this, he headed to Florida, and was aboard a troop transport, when he was discovered and put ashore. He became ill with malaria caught in camp, and by the time he recovered, the war was over. McCarthy then entered law school at the University of Georgia. To pay for school, he took a job as the school's football coach. During his two seasons, 1897 and 1898, McCarthy's team compiled a record 6–3.