Primates are common zoo exhibits. Many species thrive in zoos, but some do not, often due to inappropriate diets. We aimed to improve zoo primate nutrition through zoo and field research and keeper training. We found that zoo diets are much lower in fiber and higher in sugar/starch than wild diets, which is associated with many health and behavioral issues. These low-fiber diets result from a misconception that all primates eat fruit and a lack of understanding of how fruit grown for humans differs nutritionally from wild fruit. Misconceptions about primate granivory, insectivory, and carnivory and the use of seeds, meat, and dairy products were also common. We now have greater understanding of primate nutrient requirements and the nutrient content of zoo foods so we know how to feed our primates better. However, convincing keepers to remove fruit from primate diets is a very tough task. To bridge the gap between our improving knowledge and traditional practices, we have delivered a primate nutrition training course across Europe. Feedback surveys show keepers are getting the message and primate diets are slowly changing, often resulting in dramatic improvements in primate health.