He was the first Sir Ernest Cassel Professor of International Relations at LSE in 1924 and one of the first professors in this subject anywhere in the world. He was also an athlete, competing in the Olympic Games several times, including captaining the British team in 1924.
On leaving LSE, Noel-Baker pursued a career in politics, and was a member of parliament from 1929 to 1931 and 1936 to 1970. During the Second World War he was parliamentary secretary of the Ministry of War Transport. He held several posts in Atlee's post-war administration and joined the Cabinet as secretary of state for commonwealth relations in 1947.