The couple, who have been married for more than 20 years, dedicated Instagram posts to one another on their “special day”.
Zeta-Jones turned 53 on Sunday (25 September) while Douglas turned 78.
The Legend of Zorro star shared two selfies of her and Douglas with her 4.2m followers on Instagram and wrote in the caption: “It’s our birthday! After 24 years of celebrating our special day together, I still look forward to it. I love you! A la votre!”
Douglas posted a throwback snap of the couple embracing in front of the Taj Mahal in Agra and wrote: “Happy birthday Catherine! I love you always and forever.”
Zeta-Jones later posted a video of her and Douglas in a helicopter flying over the ocean and added: “All smiles as we start our birthdays! Let the games begin!”
Famous friends including Viola Davis, Isabelle Amara, and Michelle Pfeiffer wished the couple many happy returns in the comments.
The pair married in November 2000 in a private ceremony in The Plaza, New York City. Douglas was previously married to Diandra Luker from 1977 to 2000, with whom he shares a 43-year-old son, Cameron.
Zeta-Jones and Douglas share two children, 22-year-old son Dylan and 19-year-old daughter Carys.
In 2013, the couple announced that they were “taking some time apart to evaluate and work on their marriage”.
The separation came after Douglas was diagnosed with Stage Four throat cancer in August 2010, while Zeta-Jones battled with bipolar disorder.
The Basic Instinct star was given the all-clear on his health a year after his diagnosis, whereas Zeta-Jones spent five days in a rehabilitation clinic in 2011.
They reconciled in 2014, with Douglas declaring that they were “stronger than ever”.
Speaking on The Ellen DeGeneres Show at the time, he said: “I’m crazy about her. I think every couple has their difficult times. The only problem is, as you may well know, we’re all in the public eye and it tends to get a little more exposed than most. But we’re back, stronger than ever.”