Yoo Sun made her acting debut in 1999 with appearances in the film Mayonnaise and in an episode of KBS2’s Hometown of Legends. In 2003, she won Best Supporting Actress at the SBS Drama Awards for South of the Sun. In 2004, she appeared in the psychological horror film The Uninvited, which earned her a Best Supporting Actress nomination at the 41st Grand Bell Awards. That same year, she received the New Star Award as well as an Excellence Award at the SBS Drama Awards for her work in Little Women and Into the Storm, respectively. In 2007, she acted alongside Hwang Jung-min and Kang Shin-il in the horror film Black House, which scored her a nomination for Best Supporting Actress at the 28th Blue Dragon Film Awards. She then bagged an Excellence Award at the 2007 SBS Drama Awards for That Woman Is Scary. In 2009, she starred in the KBS2 family drama Sons of Sol Pharmacy House, which gave her two Excellence Award trophies. In 2010 and 2011, she clinched back-to-back Best Supporting Actress nominations at the Blue Dragon Film Awards for the movies Moss and GLove. In 2012, she was nominated for a Top Excellence Award at the MBC Drama Awards for her performance in the sageuk The Horse Healer.

Yoo Sun attended the Korea National University of the Arts. In May 2011, she tied the knot with her boyfriend of 10 years. In February 2014, she gave birth to a daughter.