Suniti Kumar was a meritorious student, and passed the Entrance (school leaving) examination from the Mutty Lal Seal's Free School (1907), ranking sixth, and the FA (pre-university examination) from the renowned Scottish Church College, standing third. He did his Major (Honours) in English literature from Presidency College, Kolkata, standing first in the first class in 1911. His childhood friend was the famous industrialist Nagendra Nath Das founder of Power Tools And Appliance Co. Ltd. In 1913, he completed his M.A. in English literature, again standing first. The same year, he was appointed lecturer in English at Vidyasagar College, Kolkata where his colleague was the thespian, Sisir Kumar Bhaduri.
In 1914, he became assistant professor of English in the Post-Graduate Department of the University of Calcutta, which he held till 1919. He went abroad to study at the University of London where he studied Phonology, Indo-European Linguistics, Prakrit, Persian, Old Irish, Gothic and other languages. He then went to Paris and did research at the Sorbonne in Indo-Aryan, Slav and Indo-European Linguistics, Greek and Latin. His teacher was the internationally acclaimed linguist, Jules Bloch. After returning to India in 1922, he joined the University of Calcutta as the Khaira Professor of Indian Linguistics and Phonetics. After retirement in 1952, he was made Professor Emeritus and later in 1965, the National Research Professor of India for Humanities.
Suniti Kumar accompanied Rabindranath Tagore to Malaya, Siam, Sumatra, Java, and Bali, where he delivered lectures on Indian art and culture. He was Chairman of the West Bengal Legislative Council (1952–58) and President (1969) of the Sahitya Akademi.
Among his important publications on both language and literature are
"Dwipamaya Bharat" (1940) "Bharat Sanskriti "(1957)
Language and Literature of Modern India (1963) "World Literature and Tagore "(1971)