Adaptations to a plant-based diet have evolved in bats on two occasions — once in the Old World family Pteropodidae and again within the New World family Phyllostomidae. Although the skulls of all plant-visiting bats exhibit adaptations for relatively large eyes, enlarged brains, and reduced molar complexity, the skulls of bats from the two families look very different. The goals of this study are to pinpoint the fundamental differences in the cranial shape between pteropodids and plant-visiting phyllostomids and to investigate patterns of diversity in cranial shape within each lineage. Analyses are based on 19 size adjusted, linear variables collected from 335 specimens that represent 71% of pteropodid and 45% of plant-visiting phyllostomid genera. Results of a stepwise discriminant function analysis indicate that differences in cranial shape between pteropodids and plant-visiting phyllostomids involve general aspects of relative braincase width, palate width and coronoid process height. Pteropodids have relatively narrow skulls and palates, and dentaries with tall coronoid processes, while the opposite is true of phyllostomids. Principal components analysis and an investigation of coefficients of variation reveal a high level of variation among the skulls of plant-visiting phyllostomids while cranial architecture among pteropodids is more conservative. This study documents patterns of morphological diversity in the skulls of plant-visiting bats. Several potential ecological and biomechanical mechanisms underlying these patterns are discussed.