Lee Jun-hyuk started acting in 2007 with an appearance in the SBS series First Wives’ Club, which won him the New Star Award at the SBS Drama Awards. In 2009, he was nominated for an Excellence Award at the KBS Drama Awards for the weekend family drama Three Brothers. In 2011, he became part of the main cast of the hit SBS series City Hunter, which earned him an Excellence Award nomination at the SBS Drama Awards. He also received Excellence Award nominations at the KBS Drama Awards for his performance in Equator Man, House of Bluebird, and Are You Human Too. In 2017, he starred in tvN’s Forest of Secrets, which was awarded the Daesang at the 54th Baeksang Arts Awards. In 2020, he took home the Best Acting Award at the 5th Asia Artist Awards for his work in Forest of Secrets 2 and 365: Repeat the Year. He also picked up an Excellence Award at the MBC Drama Awards for his portrayal of the leading role in the latter.

Lee Jun-hyuk enlisted for his mandatory military service in June 2012. He was discharged in March 2014.