Charles, the heir to Queen Elizabeth II, and his eldest child William released a video message warning of the "grave threat" to some of the world's most treasured species.
The royals are attending a series of conservation events this week, including a London Conference on the Illegal Wildlife Trade hosted by the British government on Thursday.
"We have come together, as father and son, to lend our voices to the growing global effort to combat the illegal wildlife trade," the 65-year-old Charles says in the recording, in which he and William sit alongside each other, both wearing suits.
The recording ends with two royals saying the phrase "Let's unite for wildlife!" in Arabic, Vietnamese, Swahili, Spanish and Mandarin, in what palace officials said was a bid to reach countries most affected by the illegal wildlife trade.
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William - who became a father in July when his wife Kate gave birth to Prince George - quit the British military last year to head up a new global conservation group called United for Wildlife.
On Thursday Charles and William will both attend the full conference at Lancaster House, a Foreign Office building in London. Charles and Foreign Secretary William Hague are both due to give speeches.
Around 50 countries have been invited to the conference.
The British government said the conference would give "leaders from across the world an opportunity to discuss the issue and agree a more coordinated global response".
Charles says the trade "now poses a grave threat not only to the survival of some of the world's most treasured species, but also to economic and political stability in many areas around the world.