1985–2005: Early life and music career Seo was born on February 27, 1985, in
Dobong District (now
Nowon District), Seoul, South Korea. She was scouted by
S.M. Entertainment and later debuted as a vocalist of South Korean
girl group,
M.I.L.K in 2001, under the label's subsidiary BM Entertainment. However, the group soon fell by the wayside due to fierce competition among manufactured bands, which led to one of the members quitting before they completely disbanded in 2003. After M.I.L.K. was dissolved, Seo attended
Dongduk Women's University, where she majored in applied
musicology to keep her dream of a singing career alive. Seo contributed songs to a few soundtracks and
SM Town compilations as a solo artist.
2006–2014: Acting debut and further roles Seo had the chance to perform in her first musical,
The Sound of Music in 2006, which she saw as the turning point in her acting career. TV police procedural
H.I.T (2007), and the
queer-themed film
Ashamed (2011). Seo first drew attention for her subtler performance in
The Duo (2011), as a neighborhood tomboy who later becomes a
gisaeng. She played her first villain in
Feast of the Gods (2012), as an extremely ambitious chef embroiled in a rivalry. Seo was then cast in leading roles for two historical dramas ''
The King's Daughter, Soo Baek-hyang (2013) and The Three Musketeers'' (2014). Seo has also frequently appeared in projects directed by her best friend, actress
Ku Hye-sun, notably in the
short film The Madonna and in the feature film
Magic, in which she had her first leading role.
2015–present: Rising popularity and continued television roles Seo said the character that most resembled her real-life personality was the foodie freelance writer in ''
Let's Eat 2 (2015), adding that she "didn't realize how much fun shooting a lively and comedic drama could be.''" The drama was Seo's first foray into the romantic-comedy genre. She was reviewed well for the part, to the point that it became a turning-point in her career. '' in December 2016 Her popularity grew rapidly after the hit romance comedy drama
Another Miss Oh (2016), in which she starred alongside
Eric Mun. She was praised for her portrayal of a girl-next-door type, and won the
Baeksang Arts Award for Best Actress. In 2017, Seo starred in the romantic-themed television series
Temperature of Love penned by Ha Myung-hee. In 2018, Seo was cast in the fantasy melodrama
The Beauty Inside which was based on the 2015
romantic comedy film of the same name. She played an actress who spends a week each month inhabiting someone else's body. She then starred in the high school television series
Black Dog: Being A Teacher in 2019 and subsequently in the
tvN drama series
You Are My Spring in 2021. In 2022, Seo starred in the
SBS legal drama
Why Her in the titular role of Oh Soo-jae, a lawyer-turned-professor and in the film
Cassiopeia as a woman who is diagnosed with
Alzheimer's disease and is slowly turning into a young child due to the loss of her memory. In 2024, Seo starred in the
mystery melodrama television series
The Trunk opposite
Gong Yoo. Written by Park Eun-young and directed by
Kim Kyu-tae, it is based on the novel of the same name by
Kim Ryeo-ryeong about two people under a one-year marriage contract and a mysterious trunk. Seo played Noh In-ji, a director of the company that arranges temporary marriages. ==Personal life==