Sumithra was born in Thrissur, Kerala to Ragavan Nair and Janaki. From her young age, Sumithra was interested in the arts. She is a classical dancer, who learnt dance from Murugappan. Murugappan was the master to actress K.R.Vijaya. Sumithra started her film career as an actress in the year 1972 through Nrithasala, a Malayalam movie. She made her debut in Tamil through Avalum Penn Thane and in Kannada through Mugiyada Kathe. Sumithra has acted with almost all the popular actors in the south such as
Sivaji Ganesan, Rajini Kanth, Kamal Hassan, Sathya Raj, Vishnu Vardhan, Mamooty and many more. She is one of the beautiful mother actresses, who were once the heroine of those sons. Bhuvana Oru Kaelvikuri, Chittu Kuruvi, Annan Oru Koyil and Mazhalai Pattaalam were some of her hit movies as the lead. She acted opposite to Rajini Kanth in Bhuvana oru Kaelvikuri and in Panakkaran, she is his mother. Similarly, she paired Kamal in Nizhal Nijamaagiradhu and acted as his mom in Singaravelan. She is married to the popular Kannada director Rajendra Babu and has two daughters, Uma and Nakshathra. Uma has already acted in Kannada and Tamil movies and settled after marriage. Nakshathra has been introduced to the cinema industry through the Tamil movie Doo.