Abstract: The micromorphology of the fruits of 21 species of Pleurospermum (Apiaceae) was evaluated for the first time in this study. The wing, exocarp, mesocarp, vascular bundle, secretory duct, commissure, endosperm, and crystals of the fruits of 21 Pleurospermum species were observed under a light microscope. The structure of Pleurospermum fruits varied greatly and the studied taxa could be divided into three groups. In group one (three taxa including P. hookeri) and group two (seven taxa including P. angelicoides), the wing margins were not wavy, the outer walls of the exocarp were flat, and the exocarp was difficult to separate from the mesocarp. Spherical crystals were present in the mesocarp in group one but not group two. In group three (11 taxa including P. franchetianum), the wing margins were wavy, the outer walls of the exocarp bulged, and the exocarp was easily separated from the mesocarp. There were no spherical crystals in the mesocarp of group three. These analyses of the micromorphology of fruits confirmed that the genus Pleurospermum is polyphyletic, that there is a close relationship between P. hookeri and P. yunnanense, and provided evidence to support the placement of P. decurrens, P. franchetianum, and related taxa into the tribe Pleurospermumeae. The results of this study also provide morphological data for further research on this genus and related taxa.