The leaf anatomical characters of Harpullia and the related genera Majidea and Conchopetalum are described in detail. Harpullia and Majidea both have stellate hair tufts together with solitary unicellular hairs, in Conchopetalum stellate hair tufts are absent. A high variability below the species level is reported for several leaf epidermal characters. Other leaf anatomical characters such as the hypodermis, sclerification of the bundle sheath extensions, and the presence of secretory idioblasts and idioblastic sclereids also show a considerable variation. Characters with a higher diagnostic value within Harpullia are the type of stomata and in certain species the presence of idioblastic sclereids in the mesophyll. Based on leaf anatomy the subgenus Otonychium within Harpullia can be distinguished by the cyclocytic stomatal type and absence of secretory idioblasts. The subgenus Harpullia is characterized by the paracytic stomatal type, which has not been recorded elsewhere within the Sapindaceae. A subdivision of the subgenus Harpullia cannot be made, because of an obvious lack of mutual correlation between the different leaf anatomical characters.