Abstract In order to study the relationships among seed yield and its components in Nigella sativa, path coefficient and factor analysis was done using some agro- morphological traits of 21 different genotypes. Genotypes were evaluated using a completely randomized design with four replications in Ardestan University Research Farms. There was a high and positive correlation between seed yield and biological yield, seed number in follicle, number of stem branches, bush height and harvest index. Stepwise regression analysis for seed yield showed that biological yield, seed number per follicle, number of stem branches and harvest index were entered in the model, respectively, and justified 45 percent of total variation of seed yield. Based on path analysis, biological yield and number of seed in follicle had the highest direct effect on seed yield. Factor analysis revealed 3 hidden factors which totally accounted for 94.12% of variations among traits. These factors were named as efficiency factor (seed yield and biological yield), yield components factor (number of stem branches and follicle number per plant) and follicle trail factor (follicle weight and number of seeds in follicle), respectively. Therefore, the research suggested that biological yield, seed number per follicle and number of stem branches had the most relative effects on seed yield and can be consider as suitable selection criteria for improving seed yield per plant in Nigella sativa.