Giant pandas are primarily herbivorous in diet, even though they belong to the mammalian order Carnivora. According to the Smithsonian’s National Zoo, about 99% of what they eat is bamboo, and they may spend 10 to 16 hours a day foraging to get enough nutrients. Their digestive tract still resembles that of a carnivore more than a typical plant-eater, so much of the bamboo passes as waste and they need roughly 70 to 100 pounds of bamboo each day.
So the short answer is mixed by definition: taxonomically they are carnivorans (bears), but functionally they are bamboo specialists with an almost entirely plant-based diet—not conventional omnivores that regularly eat both plants and animals.