Seymour's teaching experience began at Yale in 1911 when he was made an instructor in history. He was made a full professor in 1918; and when he eventually left teaching, he had risen amongst the faculty to become
Sterling Professor of History (1922–1927). He taught history at Yale from 1911 though 1937, when he became president of the university. Seymour was elected to the
American Academy of Arts and Sciences in 1938 and the
American Philosophical Society in 1939. At age 52, Seymour succeeded
James Rowland Angell as the university's 15th president in October 1937. After his retirement in July 1950, he would be succeeded by
Alfred Whitney Griswold. After his retirement as president, Seymour continued his involvement with the university as curator of the papers of
Edward M. House at the Yale University Library. He died in
Chatham, Massachusetts in 1963 after a long illness. His son, Charles Seymour Jr., was a professor of
art history at Yale. ==Selected works==