Umapati Kumar is best remembered for his long and cherished career with Mohun Bagan A.C. He joined the club as a youngster in 1916 and would continue to don the Green & Maroon jersey for more than two decades. He played in alongside some of the stars from Mohun Bagan’s famous 1911 IFA Shield winning team, as well as later icons like Gostha Pal and Dr. Sanmatha Dutta. He was the Captain of Mohun Bagan team from 1927 to 1929. He was a brilliant footballer who was famous for his through pass, ball control and dribbling. He retired from Mohun Bagan in 1936.

Umapati Kumar was also a regular participant in exhibition matches that took place in Kolkata like Indians vs Europeans and Civilians vs Military. Kumar captained the Indian team in these matches for four consecutive seasons and the Civilian team (which would also contain Europeans) for two consecutive seasons in 1926 and 1927. He was also an integral part of the IFA XI which toured Ceylon (Sri Lanka) and South Africa in 1930s.

In Mohun Bagan Umapati Kumar won Coochbehar Trophy six times and a host of other trophies. He was also the captain of the side which reached the 1923 IFA Shield final.

After his retirement, he was the Football Secretary of Mohun Bagan. He also was the Vice President of Mohun Bagan from 1959 to 1979. From 1980 to 1990, Umapati Kumar performed his duties as the President of the club. He received the “Mohun Bagan Ratna” posthumously in 2006.