Rahasya was born in Chikkamagalur district of Karnataka. Her father Shashidhar is a coffee estate owner and mother Nanda is a housewife. She completed her schooling in Bangalore and is an alumna of St. Aloysius College in Mangalore.
Deepa Sannidhi was in her first year in architectural engineering when she received a film offer for Saarathi, and dropped out of college to pursue a career in films. She also has some prior experience in modelling and has completed a one-year course in jewellery designing. During her acting career, Deepa simultaneously pursued a degree in English Literature through Distant Education.
She took part in the audition tests conducted by the Saarathi film team and was selected to play its lead role after undergoing two rounds of tests. While shooting for Saarathi, she signed her second film Paramathma directed by Yograj Bhat, which released a week after Saarathi. Paramathma also went on to become a successful venture. Deepa was chosen as the Promising Newcomer Female for Saarathi and Paramathma in The Bangalore Times Film Awards 2011. Her only 2012 release was Preetham Gubbi's Jaanu. Rediff in its review called it "Deepa Sannidhi's film all the way".
In 2014, she was first seen in Endendu Ninagagi as Soumya, "a very bold, in-your-face, today's girl". She stated that the role was "quite challenging because this is not me" but that she loved playing it. In 2015, she made her Tamil film debut in Enakkul Oruvan, a remake of Kannada film Lucia, in which she will play the character that Shruthi Hariharan did in the original. Even before her Tamil debut she signed up her next Tamil film, Vishnuvardhan's Yatchan.
|Denotes films that have not yet been released|
|1||2011||Saarathi||Rukmini||Kannada||Won, Suvarna Award for Best Female Debut|
Won, The Bangalore Times Film Award for Most Promising Actress
|2||Paramathma||Deepa||Nominated - Filmfare Award for Best Actress - Kannada|
|6||2015||Enakkul Oruvan||Divya||Tamil||Nominated, SIIMA Best Debut Actress|
- "Deepa Sannidhi's birth name is Rahasya – The Times of India". The Times Of India.
- "Mangalore: Kannada Movie 'Sakkare' – All Set for Sweet Taste of Success". Archived from the original on 26 May 2012. Retrieved 25 May 2012.
- 'I wasn't serious about pursuing a career in films' – Rediff.com Movies. Rediff.com (1 June 2012). Retrieved on 2015-05-27.
- "Deepa Sannidhi". Facebook. Retrieved 1 May 2012.
- "I want to see myself on screen: Deepa Sannidhi – The Times of India". The Times Of India.
- "All work and no play for Deepa – Times Of India". Articles.timesofindia.indiatimes.com. 16 June 2011. Retrieved 1 May 2012.
- "The Bangalore Times Film Awards 2011". The Times Of India. 21 June 2012.
- Review: Jaanu is and average fare – Rediff.com Movies. Rediff.com (1 June 2012). Retrieved on 2015-05-27.
- "Celebrate young love with Endendu Ninagaagi – The Times of India". The Times Of India.
- 'I loved my role in Endendhu Ninagaagi' – Rediff.com Movies. Rediff.com (13 April 2014). Retrieved on 2015-05-27.
- "Deepa Sannidhi in Lucia's Tamil remake – The Times of India". The Times Of India.
- Kannada girl Deepa Sannidhi for Arya – The Times of India. Timesofindia.indiatimes.com (18 May 2014). Retrieved on 2015-05-27.
- Deepa teams up with Darshan again