In order to study the effects of nitrogen application rate and timing on grain yield, phyllochron and leaf appearance rate of corn (Zea mays L.), an experiment was conducted as split plot based on randomized complete block design with three replications at the Research Farm of University of Mohaghegh Ardabili, Ardabil, Iran during 2009 growing season. Nitrogen rates were arranged in main plot with four levels including: 0, 75, 150 and 225 Kg N ha-1 and nitrogen application timing in sub plots at three levels: (1/3 in planting + 1/3 in 8-10 leaf stages + 1/3 in tasseling), (½ planting + ½ in tasseling) and (½planting + ¼ in 8-10 leaf stages + ¼ in tasseling) as T1, T2 and T3 respectively. The results showed that phyllochron was significantly affected by nitrogen rate, application timing and interaction of rate × nitrogen application timing. Phyllochron was decreased with increasing nitrogen rates, but the reverse was true for leaf appearance rate. Leaf appearance rate in T1 nitrogen application was more than the other methods. The highest leaf appearance rate and the least phyllochron belonged to treatment of 225 Kg N ha-1 and T1 nitrogen application timing. The highest grain yield (7928.6 Kg ha-1) belonged to treatment of 225 Kg N ha-1 and T1 nitrogen application timing. Thus, it seems that in order to increase the grain yield and leaf appearance rate, 225 Kg N ha-1 should be applied as T1 in conditions of Ardabil climate.