In a statement, the pair said that they remain "caring friends with admiration and respect for each other." They got married five years ago at Joel's mansion on New York's Long Island.
A representative for Joel did not immediately respond to the question of whether the couple were getting a divorce.
The marriage was the third for Billy Joel. His marriage to Elizabeth Weber ended in divorce in 1982 after nine years. He married his second wife, model Christie Brinkley, in 1985; they divorced in 1994.
It was Katie Lee's first marriage.
Joel, 60, and Lee, 27, were married in 2004. Joel is the multimillion selling musician behind such albums as "The Stranger," "52nd Street" and "Storm Front." Lee is a food critic and chef. She hosted the first season of Bravo TV's "Top Chef."
He recorded the song "All My Life" as an anniversary gift to her two years ago.