Mapping of groundwater nitrate can be useful in management of groundwater resources. The objectives of this study were to analyze the spatial variability of nitrate and to map its contamination in the Lordegan aquifer and to evaluate the variations in nitrate variability and mapping during a year. Then 32 wells were sampled four times during 2010. Seasonal nitrate concentrations remained constant at 10 mg/l and the maximum concentration was 19 mg/l thus always remaining below the WHO limit. For mapping, the inverse distance weighting method was preferred over kriging. The north of the aquifer (near Khardan village) always had the highest nitrate concentrations (19 mg/l) probably due to the presence of shale and marl formations that contain exchangeable nitrate and ammonium as well as due to leaching of nitrate from agricultural soils. Lowest concentrations of nitrate (four mg/l) were always seen in the southwest of the aquifer.