After finishing education Mahadevan and his school friend S. Rajandram joined Beer and Co. as guarantee brokers.[2] Mahadevan was appointed manager of the company after it was taken over by Dodge and Seymour in 1935.[2] He became general manager of the National Carbon Company in 1939.[2]
After Dodge and Seymour ceased trading in Ceylon Mahadevan and Rajandram established several businesses to take over its client base: Mahadavans Limited, Rajandram Limited, Stirling Products and Maharaja Distribution.[2] The Maharaja building in Banshall Street, Colombo was completed in 1953.[2]
Mahadevan was a secretary of the Hindu Educational Society, which built Colombo Hindu College, and a trustee of the Maharaja Trust.[2][3] He died on 23 December 1957 after a heart attack.[2][4]