Lee Jun-ki began his entertainment career as a model before transitioning into acting. He landed his first major role in the 2005 historical drama film The King and the Clown, which won him numerous acting trophies including Best New Actor at the 42nd Baeksang Arts Awards. That same year, he was cast in the popular SBS romantic comedy My Girl. In 2007, he starred in the action-romance drama Time of Dog and Wolf, which earned him an Excellence Award at the MBC Drama Awards. In 2008, he took home a Top Excellence Award at the SBS Drama Awards for his portrayal of the titular character in Iljimae. In 2013, he bagged another Top Excellence Award at the 2nd APAN Star Awards for MBC’s Two Weeks. In 2016, he was paired with IU in the SBS sageuk Moon Lovers: Scarlet Heart Ryeo, which scored him a Daesang nomination at the SBS Drama Awards. Also in 2016, he made his Hollywood debut in the film Resident Evil: The Final Chapter. In 2020, he led the tvN series Flower of Evil, opposite his Criminal Minds co-star Moon Chae-won.

Aside from acting, Lee Jun-ki also ventured into singing and released his debut single album My Jun, My Style in April 2007. This was followed by several more albums such as 2014’s Exhale and 2018’s Delight.

Lee Jun-ki enlisted for his mandatory military service in May 2010 and was discharged in February 2012. He previously dated actress Jeon Hye-bin, whom he co-starred with in the 2014 KBS2 sageuk Joseon Gunman.