The Prince of Wales is scheduled to attend the COP30 climate summit in South America in the coming weeks, according to palace sources.
The father and son duo appeared together on Thursday evening at a reception leading up to the environmental conference, which is scheduled to take place in the Amazonian city of Belem.
The King and Prince were present at the museum gathering, marking an rare public appearance together at a environmental conference preliminary meeting organized in partnership with the British authorities.
King Charles has been a consistent supporter of protecting nature - and Prince William has taken on the baton, with his own Earthshot awards, which will be hosted in Rio ahead of the UN meeting.
Royal sources have characterized the Prince's participation at the forthcoming conference as taking on an important role in "environmental negotiations".
The monarch and his heir, making a joint entrance in the royal vehicle, were introduced to attendees such as conservation experts, scientists, climate change campaigners, diplomats and government officials.
This engagement involved presentations in concert with French leader Macron of France and other global statesmen at the Blue Economy and Finance Forum in Monaco earlier this year.
The climate conference will dovetail with the prince's own climate innovation prizes, which will wrap up in the Brazilian city the previous day he joins the COP summit on the sixth of November.
Last week the prince referred to the award contenders as "contemporary champions".
King Charles has been a key figure at past COP meetings, providing the introductory remarks in Dubai for the 28th Conference of Parties, including the observation: "The Earth does not belong to us, we belong to the Earth".
"Throughout my life I've dedicated a large proportion of my life trying to warn of the survival risks confronting humanity over climate change, climate change and species extinction," the monarch informed delegates.