Thyagarajan lives in south Chennai and first came to prominence because of his exploits as a high-ranking karate exponent. He continues to be associated with the sport. He has been a prominent face of the Congress in the city and said to be aligned with former union minister P. Chidambaram.
He was a councillor and became Mayor-in-charge in Chennai under controversial circumstances. He joined the AIADMK, was at the centre of more controversies, went underground and rejoined the Congress later.