In 2004, Lee was cast in her first leading role in the Im Sung-han drama Lotus Flower Fairy (also known internationally as Heaven's Fate[5]), in which she played the pure-hearted daughter of a shaman who becomes alienated by her family and society after her identity is revealed.

In Green Rose, her character falls in love with a man who gets framed for the attempted murder of her father; years later, she becomes slowly convinced that a doppelgänger is in fact, her boyfriend whom everybody had assumed was dead.

In My Girl, she played a lovable con artist who agrees to act as a hotelier's long-lost cousin in order to fulfill his grandfather's last wishes.

Lee played the last living daughter of a once-respected clan in the countryside whose traditional feminine virtues is put to the test when the son of a rich investor demands that she sell her ancestral house to him.

[8] In 2008, she starred in Robber, in the role of a young widowed single mother who is targeted by a con man for her savings, but he falls in love with her for real.

Later that year, Lee was originally cast as the heroine in the inter-generational epic East of Eden, set against the backdrop of a coal mining town in Taebaek through the 1960s until the present.

Though the drama was a hit, as it went on, Lee's screen time became drastically reduced in favor of other storylines, such that she decided to leave the show in episode 40.

Early in the series, some viewers criticized her for having pristine makeup and manicured nails despite portraying a slave on the run, for allegedly wearing a wrist watch onscreen, and her supposedly "inappropriate and gratuitous" cleavage exposure when her hanbok top was removed in an attempted rape scene.

In 2011, Lee played an antiheroine with a traumatic past who lies and manipulates her way up the hotel executive ladder and into the hearts of two powerful men in Miss Ripley.

"[17] Lee's character was inspired by Shin Jeong-ah, a former curator convicted for fabricating her academic credentials and embezzling funds, and the title references the Hollywood film The Talented Mr.

[18] Lee, who is fluent in English and Mandarin, and has a significant fan base in China with more than six million followers on her Weibo microblog, made her Chinese television drama debut in 2012.

[31] Lee was next cast as a top actress forced to marry an actor she hates in the Korean-Chinese drama Best Couple; it is the first TV series produced by Chinese e-commerce company Alibaba and aired in China in early 2016. and recorded more than 100 million views.

[40] In December 2013, Lee filed defamation charges against Internet users who spread malicious rumors claiming she had been involved in an upscale celebrity prostitution ring.