Charles said both he and his wife, Camilla the Duchess of Cornwall, will depart on Monday with a sense of regret.
"The welcome we received was so wonderfully warm and friendly and special that I promise you we shall leave here tomorrow with immense regret, but also with the shouts of welcome ringing in our ears."
The prince and duchess have been busy since arriving on Saturday night, heading straight into official functions.
On Sunday the pair attended a cultural ceremony in the city and visited a coastal village and an orchid garden.
In PNG's gruelling 35 degree heat, Charles, as colonel in chief of the the Royal Pacific Islands Regiment, presented the battalion with new colours.
Governor-General Sir Michael Ogio told the assembled guests Queen Elizabeth was an important unifying figure for the 37-year-old nation.
"Her Majesty's 60-year reign can be put in a PNG perspective," he said.
"It is longer than the average life span of our people, and it is 23 years longer than we have enjoyed nationhood.
"Governors-general come and go, prime ministers come and go, but Her Majesty remains and remains as widely and genuinely respected as ever ... also (serving) as a source of unity for our diverse nation."
At Sunday's dinner Prince Charles presented diamond jubilee medals celebrating the Queen's 60th anniversary on the throne to Prime Minister Peter O'Neill, deputy opposition leader Sam Basil and other dignitaries.
Also at the official table was Sir Michael Somare, PNG's first prime minister after independence from Australia in 1975, when the young nation also elected to join the Commonwealth.
Throughout the meal, the duchess and Mr O'Neill were seen in frequent and deep conversation.
The royal couple were given a choice of starters: either pumpkin and sweet potato soup with smoked paprika croutons, or a duck confit terrine with onion marmalade on a toasted brioche.
For mains they could choose between beef tenderloin with vanilla mash or seared salmon with an asparagus, roasted pimento, saffron and black truffle risotto.
Dessert was a Pacific Island tasting platter of mango and passionfruit cheesecake, kiwifruit pavlova as well as bush lime tart accompanied by a paw paw and limoncello salsa.
On Monday morning Charles will tour a youth centre while the duchess will visit a women's refuge.
The royal couple is scheduled to depart for Australia on Monday, before heading to New Zealand where Charles will celebrate his 64th birthday on November 14.
-AAP
