Onobrychis is one of the important Fabaceae genera, which is widely used in animal feeding. In the current study, we used the fruit morphological characteristics as a taxonomic tool to resolve taxonomic complexity in the genus. Mature fruits of 20 Onobrychis taxa were evaluated using the light microscopy and Scanning Electron Microscopy. We used MVSP and PAST software for statistical analyses. Results indicated the quantitative characteristics such as fruit length, width and length/width ration differed among the taxa, and ANOVA test showed a significant difference for all of them. Moreover, the qualitative features, such as fruit shape, exocarp sculpturing pattern, exocarp indumentum type and color, fruit margin shape, and fruit base shape differed among the taxa. However, some of them such as fruit shape and exocarp indumentum type and color were more variable than others (e.g. exocarp sculpturing pattern). According to these findings, we concluded that the types of indumentum on the exocarp surfaces was not the same among taxa of each section, moreover species of different sections had the same indumentum type. Although, it was a diagnostic characteristic for identification of O. amoena subspecies, indumentum type lacks taxonomic value at section level. The more frequent type of fruit margin was plumose. However, this feature was more variable among Hymenobrychis taxa, rather than other sections. The fruit margin type detected as a diagnostic trait for identification of two subspecies of O. amoena. Meanwhile, margin type lacks taxonomic value at both section and species levels, due to its identical form among most tax
