Astragalus with more than 800 species is one of the largest plant species in Iran and most of its species are medicinal and native. In this study, karyotypic characteristics of 21 populations from 13 species including A. vegetus, A. iranicus, A. vanillae, A. chrysostachys, A. glycyphyllos, A. bombycinos, A. campylorrhynchus, A. macrourus, A. caragana, A. ebenoides, A. pseudocyclophyllus, A. stevenianus and A. jodostachys were examined and compared. The results showed that there was a significant difference between the populations in terms of all measured traits (TL, LA, SA, AR, CI, TF%, DRL, LA% and SA%), except for traits A₁ and A₂. Population 25786 of A. vegetus species from Khorasan with average length of 4.51 μm had the highest total chromosome length and population 13764 of A. vanillae species from Qom with 2.67 μm had the lowest mean total chromosome length. According to the values of AR, CI, TF%, A₁, A₂, DRL, LA% and SA%, population 3421 of A. vegetus species is the most asymmetric and population 29586 of species A. campylorrhynchus had the most symmetrical karyotype.