After graduating from National School of Drama, he did theatre for next four years, until he was offered a role in Gandhi by Richard Attenborough. Over the years, as a director, he has done over 74 plays and serials, including Mohandas B.A.L.L.B., Wah Bhai Wah, Sahabji Biwiji Ghulamji and Drishtanth, Kanak Di Balli, Albert's Bridge and Panchvan Savaar.
He made his film debut with Shyam Benegal's film Arohan (1982). Following that he played the role of Mahatma Gandhi's second secretary, Pyarelal, in the Richard Attenborough film Gandhi in 1982. Later he dubbed for Ben Kingsley in the Hindi version of the film.
Thereafter he appeared in a string of art films that came under the parallel cinema category, with leading art films directors, starting with Shyam Benegal's Mandi (1983), Kundan Shah's comedy Jaane Bhi Do Yaaro again in 1983. This was followed by Saeed Akhtar Mirza satirical Mohan Joshi Hazir Ho! (1984), Mrinal Sen's Khandhar (1984), and Vidhu Vinod Chopra's suspense thriller Khamosh in 1985. He appeared in many art films, many of which went on to win National Film Awards.
In 1986, he switched to television, with the role of Karamchand jasoos(detective) in the detective-comedy, Karamchand, also starring Shushmita Mukherjee. Over the years he has been seen in numerous TV serials, including, Kab Tak Pukaroon (Doordarshan) Zabaan Sambhaal Ke (a remake of the English TV series, Mind Your Language), Lifeline with Vijaya Mehta, Neem ka Ped and finally comic interludes in Philips Top 10.
Meanwhile his tryst with art cinema continued, as he starred in films like Chameli Ki Shaadi (1986), Ek Ruka Hua Faisla (1986), and Yeh Woh Manzil To Nahin (1987). In 1987, his comic side was visible again in the commercial action film Jalwa, also starring Naseeruddin Shah.
His first National Film Award came with the 1989 film, Raakh, which also starred Aamir Khan.
He starred in the classic Punjabi film Marhi Da Diva (1989). He featured in the 1992 Mani Ratnam film Roja directed. (Roja was made in Tamil and later dubbed in Hindi, Marathi, Telugu and Malayalam.)
His strongest performance in the early part of his career came from his lead role of struggling scientist in the film Ek Doctor Ki Maut (1991), for which he was awarded the 1991 National Film Award – Special Jury Award.
In 2000 he returned to television with the serial Office Office a satirical take on the prevalent corruption in India.
In 2003 he appeared in Maqbool, Vishal Bhardwaj's adaptation of Shakespeare's Macbeth. His antagonistic performance as the short-statured, potbellied, shuffle-footed Abbaji in Maqbool got him the 2004 National Film Award for Best Supporting Actor. Meanwhile, he released films like The Blue Umbrella (2005), Dus (2005) and Halla Bol (2007). In 2006, he started to be seen again on TV. In the TV series, Naya Office Office, a sequel to his previous series Office Office.
On 11 January 2013, the Vishal Bharadwaj directed film Matru Ki Bijlee Ka Mandola starring Kapur was released.Mausam (2011) Starring Shahid Kapoor, Sonam Kapoor, Jaspal Bhatti
Mohandas B.A.L.L.B. (1998)
Mungerilal Ke Haseen Sapne (1989-1990)
Zabaan Sambhalke (1993) .... Mohan Bharti
Neem ka Ped (1991) .... Budhai Ram
Lifeline with Vijaya Mehta
Office Office (2000) .... Musaddilal
Discovery Of India
Tehreer.... Munshi Premchand Ki – Godaan by Doordarshan (2004)
Kab Tak Pukaroon
Naya Office Office (2006–2009)
1989 National Film Award for Best Supporting Actor, Raakh
1990: Nominated: Filmfare Best Supporting Actor Award, Raakh
1991: National Film Award – Special Jury Award: Ek Doctor Ki Maut
2002: Indian Telly Award for Best Actor in a Comic Role for Office Office
2003: Indian Telly Award for Best Actor in a Comic Role for Office Office
2004: National Film Award for Best Supporting Actor, Maqbool
2005: Filmfare Critics Award for Best Actor, Maqbool
2006: Nominated: Filmfare Best Villain Award for Dus
2007–08 Best Actor National Award by Journalist Association of India