A factorial experiment based on a randomized complete block design with three replications was carried out in order to study the effects of tuber size, nitrogen fertilizer and harvest date on yield and yield components of potato. This experiment was conducted in a grower’s farm in Uraki village located in Chabahar city, in 2011. In this experiment, the treatments were two levels of tuber size (smaller and larger than 35 mm), four levels of nitrogen fertilizer (0, 60, 120 and 180 kg ha-1) and two levels of harvest date (105 and 112 days after emergence). The results of analysis of variance indicated that effects of tuber size, nitrogen rate and tuber size × nitrogen rate interaction effect were significant for all of the studied traits at 0.01 probability level. Effect of harvest date was significant on total tuber yield, number of large tubers, tuber yield and dry matter. The results of this experiment indicated increasing nitrogen up to 120 kg ha-1,increased total tuber number, number of large tubers, tuber yield and dry matter. But using up to 180 kg of nitrogen per hectare reduced these traits. According to the results of this research, it seems that under our experiments condition, tuber size larger than 35 mm, using 120 kg nitrogen per hectare which harvested 112 days after emergence date of tubers (1st of April) produced 41500 kg ha-1 tuber which is suitable to gain the highest yield of tubers for planting the 'Sante' cultivar.