Members of Chiroptera (i.e. bats) possess a huge diversity of diets, which include insects, fish, amphibians, reptiles, birds, mammals, fruits, flowers, nectar, pollen, foliage, and blood. Of bats, approximately 70% of bat species are insectivorous, while only three species of bats (i.e. vampire bats) feed exclusively on blood. Vampire bats are the only group of mammals that drink blood, which appear to be unique and have become an attractive animal model to study dietary shift in mammals. Here we review studies on morphology, physiology, behavior, sensory systems, and gut microbiota in vampire bats, and highlight their adaptive traits of dietary specializations. Following the release of a high-quality genome sequence of the common vampire bat, we will have opportunities to explore functional changes of diet-related genes in vampire bats, aiming to dissect the molecular basis of dietary shift in animals. This review will be helpful in future studies of dietary changes in vampire bats and other animals.