This experiment was conducted using three synthetic cultivars and their seven parental populations at two different conditions including: non-stress and drought stress. The experiment was carried out using randomized complete block design with three replications at the Research Field of Aboureyhan Campus, University of Tehran, Iran, in 2013. Analysis of variance showed that there were significant differences between genotypes for all traits in two experiments. The highest seed yield in normal irrigation belonged to medium-maturity synthetic cultivar and Meshkinshahr with 2357 and 2208 kg.ha^-1, respectively. However, in drought stress condition the highest seed yield obtained from Meshkinshahr and medium-maturity synthetic cultivar with 1091 and 1081.5 kg.ha^-1, respectively. Genotypic correlations in non-stress condition between seed yield with umbel diameter (r=0.79^**), number of umbels (r=0.94^**), number of umbellate (r=0.89^**) and number of seed umbel^-1 (r=0.89^**) were positive and highly significant. In drought stress condition condition also the genotypic correlation between seed yield with umbel diameter (r=0.96^**), number of umbels (r=0.77^**), number of umbellate (r=0.86^**) and stem diameter (r=0.85^**) were positive and highly significant. Results of stepwise regression analysis revealed that in non-stress conditions number of umbels, number of umbellate, number of seed umbel^-1 and stem diameter, and in drought stress conditions number of umbels, stem diameter and number of nodes were identified as independent variables that explained variations in seed yield. Path analysis for seed yield also indicated that in both non-stress and drought stress conditions number of umbels had the highest direct positive effect. It is concluded that in normal and drought stress conditions, number of umbels is the most important trait for selection of fennel genotypes with high seed yield.