Karmarkar started his acting career through Marathi theatre and various cameos on television and commercial advertisements he appeared in his debue marathi film Name Nishpaap with legendary marathi actor Yashwant dutt,Vivek Apte,Suhas Joshi. His first major role came in the show Ghar Ek Mandir directed by Ekta Kapoor. He became popular for his role of Om Agarwal opposite actress Sakshi Tanwar in the show Kahaani Ghar Ghar Kii. The show aired on Star Plus and started in 2000. After the script killed the character, Karmarkar was no longer seen in it. But due to later changes in the script, the character was retrieved and he was seen playing the same role in 2007. He then went on to play various roles in TV shows. His 2006 role in the show Saarathi was of a business tycoon, inspired by Sabeer Bhatia. In 2012, he joined the popular show Uttaran playing a negative role of Tej Singh.

Karmarkar also secured small roles in Bollywood film. He has also played roles in Marathi films and plays. In 2006, he was seen playing a comedy role opposite actress Bhavana Balsavar in the play Merra Naam Joker. The play was directed by Shubha Khote. He played the lead role in the Hindi play Bas Itna Sa Khwab Hai...! opposite Shefali Shah in the year 2010. The play was directed by Chandrakant Kulkarni. For his role in the film Kshanokshani he also won the Maharashtra State Film Award.