The former opposition leader and avowed republican says he is not surprised by the warm and enthusiastic welcome "cheerful and hospitable" Australians have given the prince in Australia this week.
"He is a young, handsome and charming prince, not a stitched-up aristocrat of the old school," Mr Turnbull wrote in a commentary piece for British newspaper The Times.
No one should underestimate the enormous affection that Australians, be they republicans or monarchists, have for the Queen herself, he said.
"But it would be wrong to imagine that Prince William's youthful charms are going to change the republican debate in Australia any more than his receiving a rapturous welcome in the US would indicate that the Americans are having second thoughts about 1776," referring to when Americans issued their Declaration of Independence, on July 4, proclaiming their right to self-determination.
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Mr Turnbull said Australian republicans had never been anti-British.
"Throughout the republican campaign leading up to the 1999 referendum we did not denigrate or criticise the Queen or any of her family, let alone the British people, in any way."
The case for a republic was based on the premise that Australia's head of state "should be one of us" and "not whoever happens to be king or queen of the United Kingdom".
Monarchy has 'faded from view'
Mr Turnbull said the monarchy had faded from view in Australia.
"We no longer see the Queen's portrait in every classroom ... our national anthem hasn't been God Save the Queen for nearly 40 years."
Even the Queen's representative, the governor-general, now always an Australian, is crowded out as prime ministers of all political complexions become more and more presidential.
The republican debate had always been about the symbols of nationhood, Mr Turnbull said.
"William may be as charming a king as he is a prince, but he can never represent Australia in the way that he will represent his own country."
The Prince is now on his way home after visiting Sydney and Melbourne during his whirlwind three day trip.
