In 1956, he entered Georgia Institute of Technology (Georgia Tech), originally intending to be an industrial engineer. The following year, he moved to Emory University, from which he graduated in 1960. Two years later, he got a law degree from the same place. He then went on to work for his granduncle, Carl Vinson, in Washington, DC, which inspired him to enter politics.
On November 7, 1972, Nunn was elected to the United States Senate, as a member of the United States Democratic Party, to replace Richard B. Russell, who had died. Nunn went on to represent Georgia from 1972 until his retirement in 1996. He was replaced by Max Cleland.