Snakes
Snakes in the chameleon's native Africa will pursue the chameleon into the trees. Climbing snakes like the Boomslang and the Vine are the main culprits. Boomslangs in particular threaten chameleons since they too spend most of their time in trees. Snakes will also take chameleon eggs.
Birds
Birds will try to pick chameleons out of tree tops. They are not as good at it as snakes because the chameleon's camouflage can make them difficult to see through the foliage. Any bird will take a chameleon, but the main threats are shrikes, coucals and hornbills. The Cuckoo Hawk in Africa is so identified as a chameleon threat that a 2007 episode of "The Wonder Pets" involved a mission to save a chameleon from a Cuckoo Hawk. Like snakes, birds are also likely to take chameleon eggs.
Man
By far the biggest threat to chameleons is mankind. Chameleons are victimized by poachers and people dealing in exotic pet trading. Pesticides on farmland have poisoned them, and deforestation has cut into their habitat. Man can also be blamed for some of the forest fires that have destroyed some of their homeland in Africa and Madagascar. According to a 2009 United Press International report, Africa lost 9 million acres of forested and agricultural land per year due to forest fires between 2000 and 2005.
Other Mammals
Monkeys have also been known to take chameleons as food, although this is not common. Chameleons and monkeys don't share the same habitat that often, and even when they do there are easier sources of food for primates.