Subramaniam was born on 30 January 1910 near Pollachi in Coimbatore district, Tamil Nadu. Subramaniam completed his early education in Pollachi before moving to Chennai where he did his B.Sc in Physics at the Presidency College, Chennai. Later he graduated with degree in law from Madras Law college, Chennai. During his college days, he started Vanamalar Sangam and published a magazine called Pithan from Gobichettipalayam along with Periyasaamy Thooran, K. S. Ramaswamy Gounder, O. V. Alagesan and Justice Palanisami and Dr. L.K.Muthusamy of Lakkapuram, Erode. His inspiration was his uncle Swami Chidbhavananda.
When the Indian National Congress split in 1969, he became the interim President of Congress (I) started by Indira Gandhi. Later, he was appointed as Minister of Finance in the union cabinet by Indira Gandhi. He advised her to devalue Indian rupee and was the Finance minister during the emergency in 1976. After the emergency, he parted ways with Indira and joined the breakaway Congress faction led by Devraj Urs and Kasu Brahmananda Reddy.
Subramaniam was an active member of the Civil disobedience movement against the British during his college days. He was imprisoned during the Quit India Movement in 1942. He was later elected to the Constituent Assembly and had a hand in the framing of the Constitution of India. He was a minister of Education, Law and Finance for Madras State from 1952 to 1962 under chief ministers Rajaji and K. Kamaraj. He was the Leader of the House in the Madras Legislative Assembly for the entire duration. He was elected to the Lok Sabha in 1962 and was the Minister for Steel and Mines. Subsequently, he served as the Minister for Food and Agriculture. He also worked as the Deputy Chairman of the Planning Commission from 2 May 1971 to 22 July 1972.
He was appointed as the union Minister of Defence by Charan Singh in 1979. He became the Governor of Maharashtra in 1990. He resigned after his criticism of the style of functioning of the then Indian Prime Minister P. V. Narasimha Rao.
A commemorative coin in his honour, was released by the Government of India in August 2010. A commemorative postage stamp was also released in his honour, in 2010.
Along with M. S. Swaminathan and B. Sivaraman, Subramaniam was the Architect of India’s modern agricultural development policy, after the success of his programme which led to a record production of wheat in 1972 termed as the Indian Green Revolution. As Minister for Food and Agriculture, he introduced high-yielding varieties of seeds and more intensive application of fertilizers which paved the way for increased output of cereals and attainment of self-sufficiency in food-grains in the country. About his contribution, Dr. Norman E. Borlaug, writes: The vision and influence of Mr. Subramaniam in bringing about agricultural change and in the very necessary political decisions needed to make the new approach effective, should never be under-emphasized. The groundwork for this advance (in the production of wheat) was solidly laid during that period (1964–67) when Mr. Subramaniam was the guiding political force instituting change.