Messing, 43, and Zelman, 44, met when they were students at New York University. They married in 2000 and are the parents of a 7-year-old son named Roman.
"Debra Messing and Daniel Zelman privately separated earlier this year after a 10-year marriage," Messing's representative told UsMagazine.com. "The decision was mutual, and they remain supportive of one another and committed to raising their son as a family."
"They have been separated the better part of the year but continue to live together in New York for Roman," an unnamed source close to the couple told the celebrity news Web site. "It's very amicable."