He did his MA in political science and LLB from Calcutta University and began his career as a clerk in Deputy Accountant General office. He taught political science in a college and also worked as a journalist for sometime, before joining politics.
Mukherjee joined the Bangla Congress headed by Ajoy Mukherjee and came to the notice of the then Prime Minister Indira Gandhi in 1969. Since then, he has never looked back, and held the plum portfolios of Finance, Defence, External Affairs in Manmohan Singh government.