Asin was born to a Syro-Malabar Catholic Nasrani family. Her father Joseph Thottumkal is an Ex-CBI officer and later managed several businesses. Her mother Seline Thottumkal, who moved settlements from Kochi to Chennai to Mumbai to live with her daughter, is a surgeon. She attended Naval Public School from LKG through X standard. She then attended St. Teresa's School in Kochi for her Plus Two education. After that she attended St. Teresa's College in Kochi, a college affiliated with MG University, where she graduated with a Bachelor of Arts degree in English Literature. She is married to Micromax co-founder Rahul Sharma.
She debuted in a Malayalam film Narendran Makan Jayakanthan Vaka in 2001, at the age of 15. Asin returned with her breakthrough film as an actress, Amma Nanna O Tamila Ammayi , her first Telugu language film, which subsequently fetched her the Telugu Filmfare Award for Best Actress. Asin's first Tamil language film was M. Kumaran S/O Mahalakshmi, super hits in Tamil cinema during 2004. After the release of Ullam Ketkumae, Asin was cited as a leading heroine of the Tamil film industry after starring in blockbuster films like Ghajini, Sivakasi, Varalaru and Pokkiri respectively. After her long-delayed venture, Varalaru, succeeded at the box office. Asin appeared in her first dual role in K. S. Ravikumar's Dasavathaaram , become one of the blockbusters.
Asin opted to move into Bollywood, her first film, Ghajini became the highest grossing Bollywood film of 2008 and sixth highest-grossing Bollywood film of all time according to net collections. Her first film of 2011 was Kaavalan which released on 15 January 2011. The film was a critical and commercial success. In 2012, she first appeared alongside Akshay Kumar in Sajid Khan's multistarrer comedy Housefull 2; it was a major commercial success. Asin has been the brand ambassador for several companies and products, and has appeared in commercials for Avon, Mirinda, Colgate, Fairever, Tanishq, Big Bazaar, Parachute, Spinz talc, Lux, Amrutanjan Healthcare, and Clinic All Clear. Asin has been endorsing Mirinda soft drinks since 2004. Her upcoming movie is Vaaliban.
In an interview during the DNA I Can Women's Half Marathon in 2012, Asin, speaking about the importance of health and the necessity of education said, “This cause is probably one of the biggest women centric issues in our country. I support the education of six children each year, five of which are girls. I have closely worked with these children and I know that if given the opportunity, women can educate themselves much better and know what is wrong or right for them. Education is a basic right and women should not be deprived of that."