In order to evaluate the effect of different nitrogen fertilizer levels on physiological traits, plant height, yield components, and seed yield of rapeseed genotypes a split-plot experiment based on a randomized complete block design with three replications was carried out at the Baykola Agriculture Research Station, Mazaandaran during 2010-11. Four levels of nitrogen, as urea fertilizer, including of 0, 70, 140 and 210 kg ha-1 were considered as main plots and four rapeseed genotypes including of L7, Zafar, RGS003 and Hyola401 were considered as subplots. The result of analysis of variance revealed that the traits, including number of days to flowering, number of days to end of flowering, number of days to maturity, plant height, siliques pods per plant, seeds per silique, seed yield and oil yield were significantly affected by nitrogen levels. Genotype effect was significant effect on all the traits except seeds per silique. Hyloa401 and Zafar respectively with 3831.2 and 3893.7 kg ha-1 of seed yield, and also 1638 and 1591 kg ha-1 of oil yield were classified at the same statistical group. Non significant interaction effects of nitrogen fertilizer application and genotypes were achieved for all of the studied traits, indicated that the trend of variation of these traits due to nitrogen levels were similar in all genotypes. A significant positive correlation of seed yield with the other studied the traits, except days to flowering, indicated that increasing of nitrogen level application made increasing of the traits and finally seed yield.