William has visited the three nations during his Caribbean tour with wife Kate, and his comments will reverberate around the region where five other countries also have the Queen as head of state.
Speaking on the penultimate night of the Cambridge's visit to the Bahamas, the future king told guests including the country's prime minister Philip Davis whatever the future holds the bonds between the UK and the nations will "endure".
"Next year, I know you are all looking forward to celebrating 50 years of independence - your golden anniversary," the duke said.
"And with Jamaica celebrating 60 years of independence this year, and Belize celebrating 40 years of independence last year, I want to say this: we support with pride and respect your decisions about your future.
"Relationships evolve. Friendship endures."
Barbados replaced Queen Elizabeth as head of state in November, and elected its first president during a ceremony witnessed by the Duke of Cambridge's father, the Prince of Wales.
William's comments are likely to be interpreted as an acknowledgement of forces already in motion, as Jamaica's prime minister Andrew Holness suggested to the couple his country may be the next to become a republic.
When he welcomed the Cambridges to Kingston on Wednesday he told them Jamaica was "moving on" and intended to "fulfil our true ambitions and destiny as an independent, developed, prosperous country".
A few days after the royals left Belize, Prime Minister Johnny Briceno's government indicated the People's Constitutional Commission, a new body, will be consulting across the country on the issue of the continuing decolonisation process.
Henry Charles Usher, minister for constitutional and political reform, told Belize's parliament on Thursday the "decolonisation process is enveloping the Caribbean region".
"Perhaps it is time for Belize to take the next step in truly owning our independence," he said.Â
"But it is a matter that the people of Belize must decide on."
