Lee Na-young started out her career as a model in 1998 before debuting as an actress that same year. In 1999, she landed her first big screen appearance in the Japanese film Eiji. In 2002, she starred with Yang Dong-geun in the MBC drama Ruler of Your Own World, which won her an Excellence Award at the MBC Drama Awards. She was also nominated for Best Actress at the 39th Baeksang Arts Awards for her work in the series. In 2004, she acted alongside Jung Jae-young in the romantic comedy film Someone Special, which gave her several Best Actress trophies, including one from the 25th Blue Dragon Film Awards. She then led the 2004 MBC series Ireland, which earned her a Top Excellence Award nomination at the MBC Drama Awards. In 2006, she worked with Kang Dong-won in the film Maundy Thursday, which scored her a Top Excellence Award at the 27th Blue Dragon Film Awards. In 2010, she received an Excellence Award nomination at the KBS Drama Awards for her work in Runaway: Plan B. In 2019, she returned to the small screen in the tvN romantic comedy Romance Is a Bonus Book.
Lee Na-young married actor Won Bin in May 2015. In December of that year, they welcomed their first child.