The couple bought it at auction in New York, for a stratospheric $379,500, TMZ reports.
The timepiece, which Christie’s had expected to go for a mere $120,000, was sold Wednesday to the couple, who submitted an anonymous bid.
Kennedy had been given the watch by her brother-in-law Prince Stanislaw Radziwill, according to the gossip site.
It’s engraved with the date February 23, 1963, and commemorates a hike the prince participated in to support President Kennedy’s goal of making Americans healthier.
It took place about nine months before Kennedy was assassinated.
Kardashian plans to wear the watch, not just keep it on display, sources told TMZ.