After their lavish wedding Friday, the couple stayed at Buckingham Palace for a reception and then departed in a military helicopter Saturday morning.
The couple, officially known as the Duke and Duchess of Cambridge, had announced they wanted privacy during their honeymoon and didn't disclose where they were going.
Nonetheless, British media was rife with speculation they were going to Kenya or Jordan, none of which were confirmed.
The Sunday Telegraph reported there had been a sudden change of plans, announced by a royal family spokesman.
"After spending the weekend privately in the United Kingdom, the Duke will return to work as a [Royal Air Force] search and rescue pilot next week," the spokesman said. "The locations of both their private weekend before the Duke returns to work and their future honeymoon, which will be overseas, will not be disclosed in advance."
It is known the couple will take a honeymoon before June 30, when they are scheduled to visit Canada for nine days.