Mamta Mohandas was born to Ambalappat Mohandas and Ganga into a Malayali family which originally hails from Kannur. She attended the Indian School, Bahrain until 2002 and is an alumnus of the School. She pursued a Bachelor's degree at Mount Carmel College Bangalore. She modeled for print ads for companies such as IBM and Kalyan Kendra and modeled on the ramp for the Mysore Maharajah and Raymonds. Mamta is trained in Carnatic and Hindustani music.
Mamta made her acting début in 2005 in the Malayalam film, Mayookham, directed by Hariharan, the film did not do well at the box office. Subsequently, she acted alongside Mammootty in Bus Conductor, with Suresh Gopi in the films Adbutham and Lanka and alongside Jayaram in Madhuchandralekha. She also played the female lead in Baba Kalyani with Mohanlal. Later that year, she débuted in the Tamil film industry, starring in the Karu Pazhaniappan-directed film Sivappathigaram opposite Vishal Krishna, which turned out to be an average grosser. In 2007 she acted with Mammootty in the blockbuster film Big B. She eventually stepped into the Telugu film industry as well, when she appeared in a supporting role in the filmYamadonga, directed by SS Rajamouli. The film became one of the biggest hits of the year. Her first release was her début Kannada film Gooli. She then starred in the film Krishnarjuna, playing the lead female role, which did not do well at the box office. In 2009, she starred in the comedy film Guru En Aalu alongside Madhavan, and the thriller Passenger, the latter was declared a surprise sleeper hit in Malayalam. Her recent movies include To Noora with Love, Varsham and Two Countries. Mamta is as an acclaimed playback singer in Indian films as well. Mamta, who is trained in Carnatic and Hindustani music, first sang playback in the Telugu film Rakhi. She was heard for the first time in her mother tongue, Malayalam, in the 2010 film Anwar. She has also recorded a song for her recent film Thriller. In the film 'Mohabath', she sang a duet with Hariharan. She sang "Iravil Viriyum" in her 2012 film Arike.
Mamta was the brand ambassador of Kochi International Fashion Week (KIWF) which was held from 4 to 7 August. She is the brand ambassador along with actress Bhavana for team Kerala Strikers for the Celebrity Cricket League (CCL) held in 2013, captained by Mohanlal, who is also one of the owners of the team, and vice-captain Indrajith. Mamta is a cancer survivor. She battled Hodgkin's lymphoma with positive energy and confidence. She is currently residing in Downtown Los Angeles as a part of her cancer treatment. Her upcoming movie is Italy Abbai Kerala Ammayi.