To study the effect of seed sowing rate, different levels of nitrogen and different sowing dates on canola cultivar Hyola401, a field experiment was conducted during 2005-2006 at Safiabad Agricultural Research Center. The design was a split split plot in a completely randomized block basis of 3 replications. Main plots consisted of 3 levels of sowing dates (6, 26 Nov and 16 Dec), sub plots of 3 levels of nitrogen (180, 220 and 260 kg/ha) and sub sub plots of 3 sowing rates (4, 6 and 8 kg/ha). Results indicated that a significant difference was observed among different sowing dates and seed sowing rates. The highest yield (4501.65 kg/ha) was obtained from 8 kg/ha of seed sowed. Application of planting date of 6 Nov, produced the highest grain yield (4777.65) while the lowest grain yield (3910.86 kg/ha) was achieved from 16 Dec. treatment, indicating that the grain yield was lower by 18.15% in the third sowing date in comparison with the first one. The interaction effect between sowing dates and nitrogen applications was significant on grain yield. Application of 260 kgN/ha at the first sowing date yielded 5138.7 kg/ha of grain. The highest oil content (93.45%) was obtained from the treatment Nov 6th sowing date. Delay in sowing date caused a, decrease in oil percentage. Delay in the sowing date also caused decrease in the number of pods per plant. The highest (325.2) and the lowest (98.13) number of pods per plant were obtained for the first and the third sowing date treatments respectively. The results reveal that from among the factors studied in this experiment, sowing date is the most important one affecting the grain yield. A sowing date of 6 Nov with an application of 260kg/ha of nitrogen, yielding the highest grain is finally recommended.