Kim So-eun began her acting career during her junior high school days with a minor role in the film ‘Two Guys’ (2004). She played bit parts in the TV dramas ‘Sisters of the Sea’ and ‘Sad Love Story’ (2005).
Kim was next seen in ‘Drama City’ (2006) and the TV series ‘Chosun Police Season1’ (2007). She appeared in the film ‘Family Matters’ and ‘Fly, Daddy Fly’ (both 2006). In 2007, she was seen in the psychological-horror film ‘Someone behind You,’ and played the daughter of the protagonist in the action film ‘The Show Must Go On.’
Kim’s supporting role in the hit TV drama ‘Boys Over Flowers’ (2009) brought her recognition. In the period TV drama ‘Empress Cheonchu’ (2009), she played the younger version (Hwangbo Soo) of the titular character, which earned her accolades. That same year, she also starred in the romantic-comedy TV series ‘He Who Can’t Marry’ (remake of a Japanese drama).
In the daily drama series ‘Happiness in the Wind’ (2011), Kim played the lead for the first time, establishing herself as popular Korean star. Her next TV series ‘A Thousand Kisses’ (2011) dealt with difference in ages in a romantic relationship. She played ‘Angel’ in the Chinese web series ‘Secret Angel’ (2012) and appeared in the Korean series ‘Happy Endings’ (2012). She portrayed ‘Princess Sukhwi’ in the period drama show ‘The King’s Doctor’ (2012-2013).
Kim participated in the reality show ‘Music & Lyrics’ (2012) and wrote a song ‘Love is Sad,’ which was later released as single and was included in ‘Feast of the God’ (2012) soundtrack. Thereafter, she appeared in the web drama ‘After School: Lucky or Not’ (2013) and co-hosted the variety show ‘Glitter’ (2013), alongside Victoria Song.
Kim was part of the reality-show ‘We Got Married’ (2014-2015) wherein she was paired with Song Jae-rim. She played a ‘girl ghost’ in the mystery-horror film ‘Mourning Grave,’ appeared in the film ‘Entangled’ and played the lead in the TV series ‘Liar Game’ (inspired from a Japanese manga), all in 2014. Next, she featured in the Chinese romantic film ‘Sky Lantern’ (2015) and starred in dual roles in the TV series ‘The Scholar who Walks eh Night’ (2015), adapted from a Manhwa.
Kim starred in the web drama ‘Falling for Challenge’ (2015), which became the most watched web drama of the year. She played the titular role in the family drama ‘Our Gap-soo (2016-2017), and further starred in the drama special ‘You’re Closer than I Think’ (2017), the fantasy series ‘Evergreen’ (2018), the TV series ‘Lonely Enough to Love’ (2020), and the romantic fantasy film ‘Are We in Love?’ (2020).