Lee began her career as part of South Korean pop girl group Fin. Lee was discovered while taking sticker pictures with her friends and was the last member to join Fin. Although originally announced as being only one episode long, it aired for four episodes on Mnet.
L debuted officially on May 22, 1998 with their first single "Blue Rain". L became one of the most popular and successful South Korean pop groups of all-time, rivaling fellow popular girl group S. Her popularity in her various activities eventually was dubbed as the "Hyori Syndrome" in South Korea, and the Korean Media nicknamed 2003 "The Year of Hyori" as she was rarely out of the news all year.
A music video was released for "Swing" (Hangul: ; RR: Geune), featuring Gary from Leessang, on March 31, 2010.
The lead single "Chitty Chitty Bang Bang" and its music video were released soon after.
During breaks in her solo music career, Lee also hosted various television programs, including Time Machine and Happy Together, which she co-hosted with Yoo Jae-suk in 2006.
On April 8, 2008, she joined KBS's Sang Sang Plus as a co-host alongside Country Kkokko members Shin Jung-hwan and Tak Jae-hoon.
The self-penned song, which features Ceejay (from Freshboyz), was released the same day as her album.
She won two Mutizen Song awards on The Music Trend for her lead single within two weeks.
In 2011, Lee released two charity songs for donation to animal shelters, "Please Stay Behind" (Hangul: ; RR: Miseukoria).It was released on March 6, 2007, and in addition to the three tracks found in the digital single, it included a reworked version of "Toc Toc Toc." It was the best-selling album for that month, selling 27,845 copies.Although her single was commercially successful, her drama was heavily penalized for violating advertising guidelines, as If in Love...During filming, part of a roof Lee was standing on collapsed.Only her foot fell through, but reportedly the fall might have been fatal if co-star Lee Dong-gun had not rescued her.