Abstract: This study was carried out at Agricultural Station of Dasht-E-Naz in North of Iran during 2003-2004 to evaluate the effects of potassium (K) and zinc (Zn) fertilizer rates on grain yield, gain oil content and some agronomical traits of three spring canola (Brassica napus L.) cultivars. Three spring canola cultivars (Hyola 401, Option 501 and PF 7045/9), three rates of potassium sulfate (K2SO4) as a potassium fertilizer (0, 50 and 100 kg ha-1) and two rates of zinc sulfate (ZnSO4) as a zinc fertilizer (0 and 10 kg ha-1) were arranged in a factorial design with four replications. The results showed that the application of potassium fertilizer significantly resulted in an increase in number of grains per pod and grain yield in all cultivars while it had no significant effect on grain oil content. However, the application of zinc fertilizer significantly increased grain oil content in all cultivars. Furthermore, the highest number of pods per branches was obtained in hybrid Hyola 401 when the highest amount of potassium (100 kg ha-1) and zinc (10 kg ha-1) fertilizers were applied. Hyola 401 also showed the best performance among cultivars in response to the application of fertilizers, implying its high ability to receive more fertilizer.