Starting her career as an Actress in Malayalam feature films in the early 1990s, she ventured into modeling and became noted, after participating and winning at several beauty pageants, which led to her debut in Bollywood. It was the film Ishq (1997 film) where she received notable attention as the sultry Dancer for the song, 'Humko Tumse Pyaar Hai' featuring Aamir Khan and Ajay Devgan and also in Bandhan (1998 film). Following appearances in over 30 Hindi films, in which she generally conveyed a glamorous image, her acting career took a turn by the mid-2000s, with her returning to Malayalam cinema and accepting substantial roles. She received critical praise and several accolades including the Kerala State Film Award for Best Actress for her performances in Paleri Manikyam: Oru Pathirakolapathakathinte Katha (2009) and Salt N' Pepper (2011).

She started her career as an Actress in the Malayalam film Anaswaram (1991), directed by Jomon, playing the female lead opposite Mammootty, after which she focused on modeling. She competed in the Miss India contest in 1994 and finished third Runner up behind Sushmita Sen, Aishwarya Rai and Fransesca Hart. She became the first Gladrags female super model in 1994 (Kelly Dorjee was the male super model) and then, Miss Asia Pacific semi-finalist in 1994 in Manila Cebu Island, Philippines. She subsequently made her debut in Bollywood and appeared in over 30 films; some of her Bollywood films include Asoka (2001), Maqbool (2003) and Corporate (2006).

Shwetha Menon was charged with insulting the Indian flag at a fashion show on 5 January 2004. The show was organized by NIFD at a resort, where Menon walked the ramp allegedly with the tricolour wrapped around her body.

Menon returned to Malayalam in 2006 with Thantra and then went on to do famous Malayalam films such as Keerthi Chakra (2006) and the award-winning Paradesi. Her performance as Sarojini, a middle-class woman who fights against extreme odds, in Madhya Venal earned her a special mention by jury chairman Bahman Ghobadi, a famous Iranian Director at the International Film Festival of Kerala. In 2010, she won the Kerala State Government's Best Actress for her portrayal of Cheeru, a village woman in the film Paleri Manikyam: Oru Pathirakolapathakathinte Katha directed by Ranjith. She won the Mathrubhumi-Amrita TV Special Jury Award and the Asianet Film Award for Best Supporting Actress for the same film. In 2011, Shweta Menon starred in the remake of Rathinirvedam, playing the titular character, originally played by Jayabharathi. In the same year, she got the Kerala State Award for Salt N' Pepper. For her next movie 'Naval Enna Jewel,' Shweta Menon has undergone a remarkable makeover as an elderly man.

Besides working in films, she has anchored several TV, stage and film awards shows. Menon rose to popularity after presenting the musical programme, Star Wars on Kairali TV in 2008. She won the Asian Television Award for Best Anchor for the same program. In Hindi, she hosted the group band based show, Razzmatazz on Zee TV with actor Arshad Warsi. The next television show she did was Dancing Queen in 2008 on Colors. In 2010, she anchored the Malayalam reality show, Honeymoon Travels on Surya TV. The show became an instant hit for Shwetha's accented Malayalam and her attempts to read from the original script without a formal learning in the language. Recently, she appeared as a contestant with her father in game show, Deal or No Deal on Surya TV. She was the anchor of the family-based reality show Veruthe Alla Bharya on Mazhavil Manorama. She has participated in popular game show Ningalkkum Aakaam Kodeeshwaran on Asianet. She is currently running popular comedy reality show Minto Goal Comedy Stars on Asianet. She has acted in many advertisements. She is currently participating in popular reality show Star Challenge on Flowers TV.

In 2010, Menon approached a local court and the Women's Commission in Kerala after the distributor of her movie tied up with Musli Power, a sex stimulant drug, to jointly promote the movie. "Met with Women's Commission regarding the Kayam ad and they offered me full backing. Thank you all and I hope justice will be done," she tweeted.

In 2011 she had filed a case against Kunnath Pharmaceuticals' managing Director K.C. Abraham for misusing stills from her film Kayam for promoting their Ayurvedic aphrodisiac Musli Power Extra. The Ernakulam central police arrested Abraham.

On 4 November 2013, she filed a case against N. Peethambara Kurup from the Indian national congress in a groping incident. Shweta later dropped her complaint against Kurup, saying the 71-year-old leader tendered a "personal apology" to her hours after she lodged the FIR against him.