Dawes was born in Marietta, Washington County, Ohio, and graduated from Marietta College in 1884 and from the Cincinnati Law School in 1886. He was admitted to the bar in that year and practiced in Lincoln, Nebraska 1887-1894. Dawes was interested in public utilities and banking 1894-1897, Comptroller of the Currency, United States Department of the Treasury 1898-1901. He was an unsuccessful candidate for the United States Senate in 1902.
During the First World War, Dawes was commissioned major, lieutenant colonel, and brigadier general of the Seventeenth Engineers.. He served with the American Expeditionary Forces as chief of supply procurement and was a member of the Liquidation Commission, United States War Department. He resigned from the Army in 1919, and upon the creation of the Bureau of the Budget was appointed its first Director in 1921. He was appointed to the Allied Reparations Commission in 1923. For his work on a program to enable Germany to restore and stabilize its economy, Dawes shared the Nobel Peace Prize in 1925.
He was Ambassador to Great Britain from 1929 to 1932, and resumed the banking business and was chairman of the board of the City National Bank and Trust Co., Chicago, Illinois, from 1932 until his death in Evanston, Illinois. He was intered in Rosehill Cemetery, Chicago, Illinois.