"Catherine has proactively checked into a healthcare facility," the representative told ABC News. "Previously Catherine has said that she is committed to periodic care in order to manage her health in an optimum manner."
Celebrity news website TMZ said the 43-year-old actress checked in Monday for a 30-day program.
A friend told People magazine the timing was right for Zeta-Jones, who is married to actor Michael Douglas, 68, to check in for what had always been part of her plan to monitor her mental health.
"This was just a good time to do it. She is in between projects," the friend said, adding Zeta-Jones is "vigilant" about managing her health.
Zeta-Jones announced in 2011 she had the bipolar spectrum disorder, which manifests in abnormally elevated or depressed moods. She said she'd been treated at a mental-health facility in Connecticut but she told ABC's "Good Morning America" in December she was "sick of talking about it because I never wanted to be the poster child for this."
Zeta-Jones and Douglas appeared together in New York April 22 for the Film Society of Lincoln Center's 40th Annual Chaplin Award Gala, honoring Barbra Streisand.
Zeta-Jones won an Oscar for Best Supporting Actress in the 2002 film adaptation of the Broadway musical "Chicago" and a Tony Award in 2010 for Best Leading Actress in a Musical for her role in "A Little Night Music."