[6][7] Lee's popularity increased after joining SBS' Good Sunday variety show Running Man, gaining the nickname "Prince of Asia" due to his large number of overseas fans.

[18][19] While filming Goddess of Fire, he participated in an energy conservation campaign alongside child actress Kim Yoo-bin.

The neo-noir film is about three friends (played by Ji Sung, Ju Ji-hoon, and Lee) whose friendship gets destroyed after getting involved in a murder case.

[23][24][25] He then returned to television with the medical melodrama It's Okay, That's Love, playing a patient suffering from Tourette syndrome, a neurological disorder characterized by repetitive, stereotyped, involuntary movements and vocalizations called tics.

[27] In 2015, Lee played the protagonist in Collective Invention, whose condition is caused by side effects from a newly introduced drug.

[29] He also starred in the two-episode drama Puck!, where he played a loan shark who joins a college ice hockey club.

[30] The same year, he was appointed ambassador of the "2015 Korea Brand & Entertainment Expo" and received commendation from the trade minister for boosting the Korean Wave industry.

[35] In 2018, Lee starred in Noh Hee-kyung's slice-of-life Live playing a police officer who tries to uphold values in everyday life and maintain justice.

[46] In 2022, Lee starred in the tvN drama The Killer's Shopping List, marking his return to the small screen after four years.