Born as Shannmathi, she had her schooling in Chennai and started modelling because of her height while in High School. Subsequently, she got offers to act in films. She debuted as heroine in the Tamil film Aatha Un Koyiley in 1991, and had appear in a number of Tamil fims thereafter, including the horror flick Rasathi Varum Naal, Government Mappilai,Chinnavar' 'and Senthamizh Paatu alongside Prabhu Ganesan in 1992.
She acted in many Telugu films which gained her enough fan following in Andhra Pradesh. After the success of Bharatheeyudu, the dubbed version of the Tamil film Indian, in which she acted as beloved daughter of Kamal Haasan, she got several opportunities to act opposite top heroes. Films like Soggadi Pellam, Merupu did not give any footage to her career.
Kasturi was the subject of a 30-minute documentary film Kasthuri: A South Indian Film star made by Richard Breyer and N. C. Rajamani in 1995. She was also a basketball player and horse rider.
Kasthuri bowed out of films after her Hindi short film The Bypass in 2003. In 2007, there were rumours that she was planning a comeback. But these rumours proved false.
Kasthuri made a come back in 2010 featuring in a item number in the hit film Thamizh Padam.