Lonkar was born in Mumbai, Maharashtra, India to Ganesh and Sharmila, and has a younger sister Janhavi. She speaks Marathi, Hindi and English fluently. She used to live in Goregaon, a far-flung suburb of Mumbai, and studied in Dr.S.Radhakrishnan Vidhyalaya and Vibgyor High, Mumbai. Her mother Sharmila works as a technician in Hinduja Hospital while her father Ganesh works with the Union Bank of India. She now lives in Milledgeville GA, and attends Georgia College & State University.

Lonkar was chosen for the role as the teenage Latika when her uncle, an acquaintance of Slumdog Millionaire co-director Loveleen Tandan, encouraged her to go for the audition; unfortunately, the scene for which she was auditioning was cut out of the film. However, when her uncle informed the director of Tanvi's ability in relation to Indian classical dance, Tandan suggested that she audition for the role of the teenage Latika. She subsequently appeared in the award-winning Slumdog Millionaire (2008) and as a member of the cast, Tanvi Ganesh Lonkar is a recipient of the 15th Screen Actors Guild Award for 'Outstanding Performance by a Cast in a Motion Picture'.

She then worked on regional Indian films, appearing in the Kannada film Teenage and signing on to star in the low budget Tamil film, Kadhal Theevu in 2012. The Tamil film did not release, but she signed on to work on another project Vidayutham in 2013. The film was released on 18 March 2016.^[3]