This study was conducted to determine the most suitable plant population and genotype of rapeseed at the Eslamabad-e-Gharb Research Station in western Iran during 2018-2020. The experiment was a factorial based on a randomized complete block design (RCBD) with three replications. Factors included four plant populations (20, 40, 60, and 80 plants m-2), and seven genotypes included four hybrids (Natalie, Rohan, Neptune, and Marathon) and three open-pollinated cultivars (Nafis, Nima, and Nilufar). The results show that the effect of the year was significant for all traits due to the difference in weather parameters over the two years of the experiment. ANOVA results shows that the effects of the plant population significantly affected plant height, the number of branches, the number of grains per pod, grain yield, grain oil, and oil yield. The effect of the genotype was also significant for all traits except oil yield. The effect of the interaction between the plant population and genotype on plant height, the number of branches, the number of grains per pod, the number of pods per plant, and 1000-grain weight was also significant. In general, open-pollinated cultivars at 60 plants m-2 and hybrid cultivars at 40 plants m-2 had higher grain yields.