Astragalus gilvanensis Ranjbar & Nouri sp. nova (Fabaceae) is described and illustrated. It belongs to Astragalus sect. Incani and is endemic to Iran. Its morphological characters, meiotic chromosome number and meiotic behavior were studied. It is a mixoploid plant with the ploidy levels 2n = 2x = 16 and 2n = 4x = 32, consistent with the proposed base number of x = 8. Although the species displayed regular bivalent pairing and chromosome segregation at meiosis, some meiotic abnormalities were observed. The meiotic irregularities included the occurrence of varied degrees of sticky chromosomes in diakinesis to metaphase, laggard chromosomes in anaphase, cytomixis in prophase to telophase, asynchronous nuclei, and binuclear cells.