Dennis Chanmugam attended S. Thomas' College, Mount Lavinia, captaining the cricket team in 1967–68.
[1] An opening bowler, he played most of his first-class cricket for Sri Lanka on three tours: to Pakistan in 1973-74, to England in 1975 for the World Cup, and to India in 1975-76.
His best first-class figures were 3 for 32 and 4 for 60 against Pakistan Universities at Rawalpindi.
[2] In September 2018, he was one of 49 former Sri Lankan cricketers felicitated by Sri Lanka Cricket, to honour them for their services before Sri Lanka became a full member of the International Cricket Council (ICC).
[3][4] His elder brother Neil Chanmugam played for Sri Lanka between 1960 and 1974.