"Catherine and Michael are taking some time apart to evaluate and work on their marriage," the rep said. "There will be no further comment."
The couple, who have two children together, haven't been photographed together since April 22 when they walked a red carpet at an event in New York City.
The movie star couple decided to take time apart shorty after Douglas returned from the Cannes Film Festival in May, People Magazine reports in its new issue . Douglas was there to support the world premiere of his latest film, "Behind the Candelabra," which debuted on HBO earlier this summer.
"They're taking a break," one individual close to the couple told the magazine.
Although living separately — Douglas reportedly on a yacht off the coast of Sardinia and Zeta-Jones at home in New York — neither has filed for divorce or a legal separation, People said.
According to a friend cited by People, "stress" from Douglas' 2010 cancer battle and Zeta-Jones' struggles with bipolar II disorder "has taken a toll on their marriage." Zeta-Jones received a second round of treatment for the disorder at a mental health facility in April.
Despite an exact 25-year age difference (oddly enough, both were born on Sept. 25), the two began dating in March of 1999 after meeting in France. They tied the knot on Nov. 18, 2000 during a ceremony at the Plaza Hotel in Manhattan.
Zeta-Jones was seen on the big screen this summer in Summit's "Red 2." Douglas will return to the box office when his buddy comedy, "Last Vegas," lands in theaters on Nov. 1.