Ji Sung began his acting career in 1999. In 2003, he was launched into Hallyu stardom with the hit SBS drama All In. His performance in the series won him an Excellence Award at the 2003 SBS Drama Awards. In 2008, he was cast in the MBC medical drama New Heart, which also served as his comeback project following his release from the military in June 2007. In 2011, he headlined the SBS workplace romantic comedy Protect the Boss, which earned him a Top Excellence Award at the SBS Drama Awards. In 2013, he bagged another Top Excellence Award at the KBS Drama Awards for his work in the melodrama Secret. In 2015, he reunited with his Secret leading lady Hwang Jung-eum in MBC’s Kill Me, Heal Me. His portrayal of the drama’s male lead character who suffers from dissociative identity disorder won him numerous acting recognitions, including the Daesang at the 2015 MBC Drama Awards. In 2017, he took home another Daesang at the SBS Drama Awards for his performance in the legal drama Defendant.

Ji Sung has been married to actress Lee Bo-young since September 2013. They met on the set of the 2004 SBS series Save the Last Dance for Me. They confirmed their relationship in 2007 and announced their engagement in August 2013. They have two children together: a daughter born in 2015 and a son born in 2019.