Singh made his acting debut in 1996 in Tere Mere Sapne which was produced under Amitabh Bachchan Corporation Limited. Later that year he starred alongside Tabu in Maachis for which he won the Filmfare Award for Best Male Debut. He appeared in several films as a leading actor which failed to do well but he had success with his lead roles in the multi-starrers Daag: The Fire (1999) opposite Sanjay Dutt, Kya Kehna (2000) opposite Preity Zinta and Josh (2000) opposite Aishwarya Rai and Shah Rukh Khan. He was nominated for filmfare awards on two occasions, in different categories.
After initial successes, his career went into a low, because of multiple dislocation of his shoulder joint, which he suffered while water skiing in Goa. Because of the pain on his shoulder, he couldn't work out or stay fit which caused him to gain weight and lose roles. His last few releases included Aamdani Atthani Kharcha Rupaiyaa (2001), Bharat Bhagya Vidhata (2002) and the delayed release Sarhad Paar which was shot in 2002 and released in 2006. All three films flopped at the box office.
In 2012, he made a comeback with the multi-starrer film Chaar Din Ki Chandni. The film featured Tusshar Kapoor, Kulraj Randhawa, Anupam Kher, Om Puri and Farida Jalal in lead roles amongst others. Chaar Din Ki Chandni received mixed response from critics, and turned out to be a flop at most places in Box office India. From 2012–present, he has joined Bollywood once again as an actor. That same year he played a small role in the English language film The Reluctant Fundamentalist. He last appeared in Zilla Ghaziabad which had been delayed for years, however got released in August 2013.
