Karan Wahi started his acting career with the 2004 "Rose Audio Visuals" television series Remix, where he portrayed the lead role of Ranveer Sisodia, the angry lover boy character, opposite Shweta Gulati. The story of the show was based on the lives of 12th-grade students in an elite school for the kids of the rich and the famous, and scholarship students from poorer families. His performance in the show won him the Indian Telly Award for GR8 Best Male Newcomer.

After a break from fiction shows, Wahi made a comeback in the 2009 Colors TV's soap opera Mere Ghar Aayi Ek Nanhi Pari as the male lead opposite Mugdha Chaphekar. By the following year, he featured in the second season of Cinevistaas Limited productions' medical drama series Dill Mill Gayye alongside an ensemble cast.

He was also seen playing the supporting role of a fun-loving guy, Rohan in mid-December 2011 on Sony Entertainment Television's romance-drama series Kuch Toh Log Kahenge. The show was the Indian adaption of the Pakistani television drama series Dhoop Kinare. He was cast alongside Kritika Kamra and Mohnish Behl. In 2012, Wahi was paired with Chhavi Pandey to play the lead in Shontara Productions' anthology series Teri Meri Love Stories. In 2016, Wahi played the lead character in &TV's Kahani Hamari...Dil Dosti Deewanepan Ki.

Wahi signed his first movie with Habib Faisal's romantic comedy film Daawat-e-Ishq in 2014. He was seen in a supporting role of a Hyderabadi boy, Amjad alongside Parineeti Chopra and Aditya Roy Kapur.[26][27][28]

He also signed to play the male lead opposite Rhea Chakraborty in the 2014 romantic drama film Babbu Ki Jawani, produced by Amritpal Singh Bindra, under the UTV Spotboy productions.[29][30][31]

In September 2015, Wahi was seen as a comedian contestant alongside Bharti Singh in Colors TV's comedy show Comedy Nights Bachao.