In 1946 Patnaik was elected uncontested to the Odisha Legislative Assembly from North Cuttack constituency. In 1952 and 1957 he won from Jagannathprasad and Surada, respectively. In 1960 he assumed the presidency of the state Congress. Under his leadership, the Congress Party won 82 of 140 seats and Patnaik (representing Chowdwar constituency) became the chief minister of Odisha on 23 June 1961 and remained in the position until 2 October 1963 when he resigned from the post under the Kamaraj Plan to revitalise the Congress party. He was the Chief Minister of Odisha at the age of 45.