Geranium sect. Trilopha (Geraniaceae) consists of seven species: G. biuncinatum, G. brevipes, G. favosum, G. mascatense, G. ocellatum, G. trilophum, and G. yemense. The highest diversity of the group is located in Iran, the Arabian Peninsula, and adjacent regions of northeast Africa with five endemic species. One species occurs in the Himalayas and another is widespread in the mountains of tropical Africa. In contrast with current literature, we consider G. yemense to be a separate species from G. trilophum, and G. brevipes also to be separate from G. ocellatum. Micromorphological features of indumentum, pollen, mericarps and seeds were investigated by SEM. Two features are present in all species of the section and give strong support to this group: a) pollen with Erodium-type exine ornamentation (first reported here), and b) fruit with twisted rostrum. A new key is provided, as well as new and detailed descriptions. Each species is illustrated and mapped and five lectotypes are designated.