When he was a senior in high school, Lim joined the theater group called Kwangto, an acronym of Kwangdae Tokkaebi referring to traditional performers and hobgoblins in Korean, where he was first introduced to theatrical performance. Lim then played the role of the pastor in The Good Doctor by Neil Simon and won the prize of best performance in the Fourth Youth Theater Festival in 2000. He also directed the play, Pay Tuition Back, at the school festival. He continues to maintain a good friendship with fellow actor Shin Dong-wook, whom he met at the time.

Lim made his first professional television debut on Magic, aired on SBS in 2004, and made his film debut in A Millionaire's First Love in 2006, followed by a series of supporting roles, notably in The Snow Queen (2006) and Boys Over Flowers (2009). He received favorable reviews for his performance as a blind Painter in episode 10 of Auction House, a 2007 TV series revolving around the art world which aired on MBC.

Lim's breakthrough came in his first leading role in the 2009 MBC series Tamra, the Island. Set in Jeju Island, Haenam in South Jeolla Province, it was a Hybrid form of TV drama that combined romantic comedy and historical fiction. It portrayed the relationship between Koreans and foreigners in 17th century Joseon. Though it received low ratings, Tamra, the Island gained a cult following. Lim later won New Actor of the Year at the 2009 Korean Culture and Entertainment Awards for his performance.

What's Up, the long-delayed musical campus drama that Lim filmed in 2010, finally aired on cable channel MBN in 2011. It was written by renowned drama scribe Song Ji-na (Sandglass) and is the story of college students learning acting and performance arts in the university's musical theatre department. Lim played the leading role of Jang Je-hun, a cynical outsider who becomes completely immersed in the world of musicals. He followed that with a supporting role as a warm-hearted homeless man with Tourette's syndrome in the film The Suicide Forecast in 2011,

In 2011, Lim enlisted for his mandatory military Service. During basic training, he fainted due to heart problems and was hospitalized for 3 months. He then completed his Service despite being given the option for an early discharge. Prior to entering military Service Lim left his agency Yedang Entertainment.

After his military discharge he moved to Blossom Entertainment. In 2013, he made his acting comeback in the lead role as a devoted brother in 2013 SBS daily drama Ugly Alert, followed by a villain role in the 2014 film The Con Artists as well as supporting roles in historical drama Shine or Go Crazy and romantic comedy series Oh My Ghost in 2015, romance melodrama Uncontrollably Fond in 2016, and fantasy romance series The Bride of Habaek in 2017.