"They're taking a break," one insider told the celebrity news website.
Word the couple have been spending time apart the past few months comes after Douglas, 68, recently battled throat cancer and Zeta-Jones, 43, was treated for bipolar II disorder.
"The stress has taken a toll on their marriage," a second source told People.com.
Neither star has officially filed for divorce or legal separation, the report said.
The couple are the parents of Dylan, 13, and Carys, 10.
Celebrity Breakups and divorces of 2014 [PHOTOS]