He was born on 5 August 1926 to A. Soliah and S.Koppammal in a village Ramanoothu, Tuticorin Dist, Tamil Nadu. Having lost his father at the age of 13, he had to take on the responsibilities of taking care of their agricultural farming. He and his younger brother S.Ramasamy were brought up by their widowed mother and aunt.
Political career
Alagarsamy first contested for Madras State Assembly in 1957 and continued to contest in all subsequent State General Assembly Elections till 1989 from Kovilpatti constituency Prior to that he contested for Unified Tirunelveli Jilla Board in 1952.
The then-unified Tirunelveli district consisted of the present Tirunelveli, Tuticorin, Kannayakumari Districts and part of Malabar and Ramnad District. He was leader of the CPI Legislative Group from 1971 till 1991 in The Tamil Nadu Legislative Assembly.
Thiru C.N.Annadurai was the Chief Minister of Tamil Nadu, when he was the Member of the Legislative Assembly in 1967 and subsequently he continued to be M.L.A, when Thiru V.R. Nedunchezhiyan, Thiru. M. Karunanidhi and Thiru M. G. Ramachandran, were the Chief Ministers of Tamil Nadu.
He held various public offices in Kovilpatti Taluk for many years. He also served on the board of directors in various co-operative organisations and banks. He was a member of the District Development Council for Tirunelveli and Tuticorin Districts. He was head of the Tamil Nadu Kishan Sabha organisation and Vice President of All India Kishan Sabha. He served in various Tamil Nadu Government Legislative Committees. He served as State Executive Committee Member and State Control Committee President of Communist Party of India.