In August 1947 he was appointed Commonwealth Secretary in the Ministry of External Affairs, From 1952-54, he was India's first ambassador to West Germany. He returned as Commonwealth Secretary in the Ministry of External Affairs (1954–55) and from 12 October 1955 to 11 April 1961 was the longest serving Foreign Secretary of India. As Commonwealth Secretary, along with V.K. Krishna Menon, Dutt was India's representative on the Political Committee at the Bandung Conference. As Foreign Secretary in the years leading up to the Sino-Indian War of 1962, Dutt was closely involved in policy formulation regarding Tibet and China. He was also involved in shaping India's response to the Suez and Hungarian crises which happened while he was the foreign secretary.