Kim Yun-jin played minor roles in MTV and ABC shows as well as in off-Broadway productions during the early days of her acting career. In 1999, she made her big screen debut in the box-office hit South Korean action movie Shiri. Her performance in the film won her several Best New Actress trophies, including one from the 36th Grand Bell Awards. In 2002, she starred in director Byun Young-joo’s erotic drama film Milae, which earned her numerous Best Actress awards. In 2004, she was cast as one of the main characters in the award-winning ABC series Lost, in which she received the Outstanding Television Actress citation at the 2006 Asian Excellence Awards. She also scored a Best Supporting Actress nomination at the 35th Saturn Awards for her work in the series. In 2008, she led the South Korean crime thriller film Seven Days, in which she was named Best Actress at the 45th Grand Bell Awards. In 2013, she took on one of the leading roles in the ABC drama Mistresses, which was based on the U.K. series of the same name.

Kim Yun-jin and her family moved to the United States when she was around 10 years old. She graduated from Boston University with a degree in drama. In 2010, Kim Yun-jin married her former manager in Hawaii.