She won the gold medal in badminton mixed doubles at the 2008 Summer Olympics with her partner, Lee Yong-dae.

After winning the medal, she announced her retirement despite many pleas from her coaches and fans at home to continue playing until the London Olympics in 2012.

[4][5] In 2002, she finished as the runners-up at the Chinese Taipei and Singapore Open in the women's doubles event with Hwang Yu-mi.

In the mixed doubles event, Lee who was teamed-up with Kim Yong-hyun achieved their best result by winning the bronze medal at the Asian Championships.

In 2004, Lee competed for Korea at the Summer Olympics in women's and mixed doubles with partner Hwang Yu-mi and Kim Yong-hyun.

[6] Lee and Hwang had a bye in the first round and defeated Cheng Wen-Hsing and Chien Yu Chin of Chinese Taipei in the second.

In the finals, she and her partner Kim Min-jung won against WR #1 Ma Jin and Wang Xiaoli, beating them 18–21, 21–12, 21–15.

In August, Lee partnered again with Lee Yong-dae in the Kumpoo Macau Open Badminton Championships, Chinese Taipei Grand Prix Gold, and World Championship, but their best finish was reaching the quarterfinals in the Chinese Taipei Grand Prix.

However, in mixed doubles, she partnered with Shin Baek-cheol, with whom she had previously played only two tournaments, but they still managed to win against two Chinese pairs (Zhang Nan and Zhao Yunlei, He Han Bin and Ma Jin) at their home court, becoming the first woman in Korean history to win both Olympic and Asian Game gold medals.