Astragalus mishodaghmontanus Ranjbar, Karamian & Nouri, a singular new species endemic to Iran, is described and illustrated. The new species belongs to subgenus Cercidothrix Bunge, section Incani DC., in Astragalus L. (Fabaceae). It is distributed in northwestern Iran in East Azerbaijan Province. Astragalus mishodaghmontanus is closely related to A. prilipkoanus Grossh. and A. hashtrudicus Ranjbar, but is distinguished by its glabrous pods with minute dark reddish dots. The IUCN conservation status of the new species is evaluated as Vulnerable (VU). Results from cytogenetic analysis indicate that A. mishodaghmontanus is a diploid species (2n = 2x = 16), with this chromosome number consistent with the proposed base number of x = 8 for the genus. Meiosis was observed as regular, with bivalent pairing and normal chromosome segregation.