At the Battle of Bristoe Station on October 14, 1863, Posey was wounded in the thigh by a shell fragment. Although the wound was not outwardly serious, infection set in. He died a month later in November, in Room 33 West Lawn at the University of Virginia, where he had lived as a law student. He was cared for by a good friend, Dr. John Davis of Charlottesville, Virginia. Posey was buried in the Davis family plot in the University of Virginia Cemetery.