The sports star and the Duke of Cambridge have recorded a public service announcement (Psa) for wildlife protection organisation WildAid.
In the video, new father Prince William calls on parents in China to reduce the demand of illegal wildlife products, since the Asian country is the principal market for ivory, rhino horn, shark's fin and other internationally outlawed items.
He says, "We must stop the demand for illegally traded wildlife products within our lifetimes or these amazing animals will be forever wiped from the planet. As a father, I want our children to know that rhinos are not just a picture in a book."
Beckham adds, "We can all do our part by sharing this message with buyers of illegal wildlife products. If you do buy ivory, rhino horn, or shark fin I urge you to stop and help us bring these senseless killings to an end."
Chinese basketball star Yao Ming also stars in the ad, as Prince William joins him in trying his hand at Mandarin.
Sharing a sentence, the pair states in the Chinese language, "When the buying stops... the killing can too."
Chinese movie icon Jackie Chan and Virgin boss Sir Richard Branson are among the other celebrities who are lending their support to the WildAid organisation.