Mahant was born in Madhya Pradesh. Her father is a Vaishnav Hindu (the reason she took the screen name Vaishnavi), while her mother is Christian. Raised as a Hindu, she converted to Christianity in the early 1990s. She is currently a born again Christian believer who is more into a relationship with God not religion.

As a child she moved to Hyderabad where she decided to become a scientist. However, while vacationing in Mumbai, she had the opportunity to appear in the Ramsay Brothers' horror film Veerana and decided to pursue acting as a profession. She subsequently appeared in Barsaat Ki Raat, Ladlaa, Daanveer and Oru Mutham Mani Mutham (a 1997 Malayalam film with actor Mukesh).

From 1998 to 2005, she played the female lead Geeta Vishwas in the superhero series Shaktimaan on Doordarshan. The show, as well as her character, got high acclaim and was considered her breakthrough role. When her journalist character Geeta Vishwas was written out of the series, fan protests prompted the producers to bring her back. In 2000, she played the role of ACP Ratna, a daring police officer in a comedy serial Raju Raja Rajasaab on Sahara TV.

She went on to play leading roles in several Tollywood movies. She played the role of Bhaskar's mother in the Sony Entertainment Television serial Bhaskar Bharti and Mayank's mother Shilpa in Miley Jab Hum Tum. She appears in Karmyudh on Doordarshan in the role of Inspector Shivangi Chauhan.

zee rishtey awards 2013- best mata pita award

Zee rishtey 2015- best maa beti award