Kim Mu-yeol began his acting career as a stage actor. Some of his notable works in theater include the musicals Thrill Me in 2007 and Spring Awakening in 2009. His performance in the latter won him Best Actor at the 15th Korea Musical Awards. Also in 2009, he joined the crime thriller film The Scam, which scored him Best New Actor nominations at the 30th Blue Dragon Film Awards and the 46th Baeksang Arts Awards. In 2010, he was nominated for Best Supporting Actor at the SBS Drama Awards for the series Wife Returns. In 2012, he received another Best Supporting Actor nomination at the 21st Buil Film Awards for the erotic romantic film A Muse. In 2017, he starred in OCN’s Bad Guys: City of Evil, which is a spin-off of 2014’s Bad Guys.

Following the controversy caused by his exemption from the mandatory conscription due to poverty, Kim Mu-yeol voluntarily enlisted in the military in October 2012. In early 2014, he once again faced backlash for his supposed lengthy sick leave due to a knee surgery. He was discharged from the military in July 2014. He married actress Yoon Seung-ah in April 2015.