Acting

Mamtha ON the set of Jawan of Vellimala in 2012

Mohandas debuted in the 2005 Malayalam film Mayookham, directed by Hariharan. The film did not do well at the box office.^[7]

Subsequently, she acted alongside Mammootty in Bus Conductor, with Suresh Gopi in the films Adbutham (2006) and Lanka (2006), and alongside Jayaram in Madhuchandralekha (2006). 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.

In 2007 she acted with Mammootty in the film Big B. She eventually stepped into the Telugu film industry as well, when she appeared in a supporting role in the film Yamadonga, directed by SS Rajamouli. She had lent her voice for a couple of songs in this film too. In 2008, she appeared in 7 films, predominantly in Telugu-language films. Her first release was her début Kannada film Gooli. She then starred in the film Krishnarjuna, playing the lead female role. Victory was her next assignment as lead actress, following which she appeared in a cameo role in her only Tamil release that year, Kuselan. Three more Telugu releases featured Mamta, including Homam, directed by JD Chakravarthy and Srinu Vaitla's King.

In 2009, she starred in the comedy film Guru En Aalu alongside Madhavan, and the thriller Passenger, sharing screen space with Dileep and Sreenivasan, respectively. The film Passenger, in which she played the role of a television reporter, became a turning point in Mohandas's career. She was initially approached to play the lead role in the 2009 Telugu dark fantasy Arundathi. She refused the offer, and the movie went on to become one of the highest grossers that year. In 2010, she worked with Jayaram in Kadha Thudarunnu^[8] directed by Sathyan Anthikkad, for which she won her first Best Actress Award from Filmfare.^[9] This film also won her the Kerala State Film Award for Second Best Actress, the Vanitha award for best actress – Malayalam, the Mathrubhumi award for best actress – Malayalam and the Asianet award for the best actress- Malayalam. Other projects in 2010 included Musafir with Rahman, Anwar with Prithiviraj, and Kedi with Nagarjuna. Mamta's first film in 2011 was the Malayalam film Race, in which she played the role of Niya, wife of a cardio surgeon Abey (Kunchacko Boban). The film failed to do well at the box office.^[10] Her next release in Malayalam was Naayika.^[11] In 2012, she appeared in her third Tamil film, Thadaiyara Thaakka, directed by Magizh Thirumeni.^[12] In 2013 she starred in Paisa Paisa with Indrajith.^[13][14] In 2014 she starred in To Noora with Love as a Muslim character.^[15]

Mohandas made a comeback to Malayalam movie industry with Ranjith Shankar's Mammooty starrer Varsham. She shared her screen space again with Dileep in Two Countries after doing My Boss with him.

In 2016, Mohandas starred opposite Mammootty in Thoppil Joppan, and in early 2017, she signed Crossroad, an anthology film in which she plays an orthodox Muslim. She also appeared in an extended cameo in Udaharanam Sujatha with Manju Warrier. In mid-2017, she signed Detroit Crossing aka Ranam opposite Prithviraj, but had to opt out because she did not have fresh dates to allocate for the project.

In 2020 Mohandas acted in the crime thriller feature film Forensic in which she played the role of police officer Rithika Xavier IPS .

Singing

Mohandas is trained in Carnatic and Hindustani music, and first sang playback in the Telugu film Rakhi, singing the title song under Devi Sri Prasad's direction, making her debut in the Telugu film industry as a singer before making her acting debut in Telugu. She went on to win the 2006 Filmfare Best Female Playback Singer Award for that song.^[16]

Subsequently, she was asked to sing several songs for composer Devi Sri Prasad, including "Akalesthe Annam Pedtha" for the Chiranjeevi-starrer Shankardada Zindabad (later dubbed as Daddy Mummy in the Tamil film Villu), "36-24-36" for the film Jagadam, "Mia" for Tulasi, and "Ghanana (Funny)" and the title song for the film King. Other music directors she has worked with include M. M. Keeravani (for her own films Yamadonga and Krishnarjuna, also Chandamama), R. P. Patnaik (for Andamaina Mansulo), Chakri (for Victory), Nithin Raikwar (for her own film Homam) and Thaman (for Jayeebhava).

In Tamil, she sang "Kaalai Kaalai" in the film Kaalai, which starred Silambarasan in the lead role. She sang "Idai Vazhi" for the comedy film Goa under noted composer Yuvan Shankar Raja's direction. Both songs featured her singing alongside Benny Dayal. 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 film Thriller. In the film 'Mohabath', she sang a duet with Hariharan. She sang "Iravil Viriyum" in her 2012 film Arike. She sang "Karuppana Kannazhagi" in the film Aadupuliyattam.^[17]