Black cumin (Nigella sativa L.) is one of the medicinal plants of Ranunculaceae family. Its seeds are containing oils, proteins, alkaloids (such as nigellicine and nigellidine), quinines (such as thymoquinone), sapiens and essential oil. Genetic diversity is important in breeding programs, so that selection depends on the existence of genetic diversity in traits. Therefore, an investigation was carried out to select the most successful Black cumin ecotype (s) and to assess the genetic diversity according to the morphological and agronomical traits in some of black cumin ecotypes at two locations based on randomized complete block design with 4 replications (in the research filed of Mohaghegh Ardabili University and Khalkhal city). The results of analysis of variance showed significant differences among studied traits in both locations, wich indicates the existance of genetic variation between ecotypes and the difference in location effect on yield and morphological traits of black cumin ecotypes. According to the results of correlation analysis, it can be concluded that the biological yield, leaf number, number of stem branches and number of flowers and follicle were the most important and effective traits affecting yield and considering that among genotypes, the biggest diversity were observed for these traits, therefore, selecting and breeding for these traits can ideally improve the grain yield. Comparison of means of grain yield showed that Karaj, Ardabil 1, Takestan, Hamadan, Lordegan ecotypes were superior to other ecotypes in both locations.