Janaki Ramachandran was born to Rajagopal Iyer and Narayani Amma in the town of Vaikom in Kerala State. She had a brother P. Narayanan who was an educationalist. Her father's younger brother was Papanasam Sivan. Janaki was a successful actress in late 1940s and starred in more than 25 movies including Mohini, Raja Mukthi, Velaikaari, Aiyiram Thalaivangiya Aboorva Chintamani, Devaki and Marudhanaattu Ilavarasi. M. G. Ramachandran had written in his autobiography that in late 1940s and in 1950,
Janaki was earning double the income he received as an actor. When M. G. Ramachandran died in 1987, she succeeded him as the first woman Chief Minister of Tamil Nadu and the Leader of the AIADMK party (which later split into two factions). Janaki Ramachandran became Chief minister in January 1988 after her husband's death, but the government lasted only 24 days, the shortest in the history of Tamil Nadu. Her ministry won the vote of confidence of the Tamil Nadu Legislative Assembly in January
1988 but the Central Government under the late Rajiv Gandhi used Article 356 of the Constitution of India to dismiss her government. Her party was defeated in the next elections held in 1989 and she quit politics after the unification of the two factions of the All India Anna Dravida Munnetra Kazhagam.