Lee Jia made her acting debut in the 2007 big-budget MBC fantasy sageuk Legend, opposite Bae Yong-joon. She won Best New Actress at the MBC Drama Awards and the 44th Baeksang Arts Awards for her work in the series. In 2008, she starred in the MBC series Beethoven Virus, which earned her an Excellence Award nomination at the MBC Drama Awards. In 2009, she was nominated for another Excellence Award at the SBS Drama Awards for Style. In 2011, she appeared in the IRIS spin-off espionage series Athena: Goddess of War, in which she bagged a Top Excellence Award at the SBS Drama Awards. In 2013, she was cast as the female lead in the SBS weekend drama Thrice Married Woman, which scored her several Top Excellence Award nominations. In 2020, she played one of the main characters in the megahit SBS series Penthouse and its sequels. She took home a Top Excellence Award at the SBS Drama Awards for her performance in the series.

In April 2011, Lee Jia’s secret marriage and divorce to South Korean music icon Seo Taiji were exposed to the public. It was revealed that the two married in 1997 and split in 2006. Prior to this, it was confirmed that Lee Jia and her Athena: Goddess of War co-star Jung Woo-sung were dating. However, it was reported that they parted ways months after the controversy involving the actress’ personal life broke out.