A graduate in law, M. R. Jayakar held several important political posts in the pre-independence era. He was a member of the Congress Commission to enquire into the Punjab disturbances in 1919. He gave up his successful practise in response to the non-cooperation call by Gandhi. His sacrifice inspired many others who boycotted government jobs and entered the mainstream of political struggle.
He led the Swaraj Party in the Bombay Legislative Council from 1923 to 1925 and was the deputy leader of the Nationalist Party in the Central Legislative Assembly from 1926 to 1930. He was one of the Indian delegates to attend the Round Table Conference. In 1937, he was made the judge of a Federal Court. He was one of the members of the Constituent Assembly. He also served the Poona University as its Vice-Chancellor.