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Lee enrolled in Seoul Institute of the Arts Acting Department class of 2011.

Lee made his acting debut in 2011, and first gained recognition from playing a rebellious student in the teen drama School 2013. Thereafter, he played supporting roles in television dramas such as My Love from the Star (2013) and Descendants of the Sun (2016). Lee gained popularity following his comedic role in Confession Couple. He was cast in his first major role in Welcome to Waikiki (2018) which was professionally successful for Lee, as he also played the lead actor in the critically well-received Children of Nobody.

Lee has also appeared in both independent and commercial films, notably Leesong Hee-il's White Night (2012) and Kim Ki-duk's One on One (2014). In 2018, he stars in two films - drama film Monsters (also known as Wretches) which tackles teenage bullying; and omnibus horror film Pension: Dangerous Encounter.

On March 8, 2022, it was reported that Lee's contract with HB Entertainment has ended. Later on March 25, 2022, Lee signed with Screening ENT after the expiration of his contract with the original agency.

After a year long break, Lee returns to acting in a major role in Marry My Husband (2024) where he plays the role of an irredeemable villain, a character that proves versatility from his usual friendly TV persona. His work in the series granted him a nomination to the 60th Baeksang Arts Award for Best Supporting Actor.

His father was the CEO of LG Innotek, Lee Ung-beom.

In April 2018, it was announced Lee was dating his Welcome to Waikiki co-star Jung In-sun. The couple was introduced by Lee's friend actor Lee Ki-woo and had been dating for a year before the news broke. However, in June 2018, the couple confirmed they had broken up.

In late 2025, controversy arose after posts alleging issues related to Lee's private life spread through online communities and social media. As disputes emerged over the authenticity of the materials and possible AI manipulation, Lee’s agency denied the claims and announced legal action for defamation.

In May 2026 media reported that Lee had been assessed additional tax after an audit of an independent one-person agency he operated while remaining with Sangyoung ENT. The amount was not disclosed. Sangyoung ENT said the assessment arose from differences in interpretation of expense-processing rules in running the corporation, that there had been no intentional concealment of income or tax evasion, that Lee had complied with tax law since his debut, and that he would pay the additional tax without delay.