Mazandaran province is located on the southern coast of Caspian Sea (46,656 km), Iran. Irrigated 2 agriculture in this region may exert serious pressure on groundwater resources. The aim of this study is to evaluate physicochemical characteristics in shallow (5-15 m) and deep groundwater (30-60 m) of 88 domestic wells over a seven-year period. The cluster analysis is used to know about interrelation of the similar characteristics of 88 sampling sites, which is formed based on three major clusters. In each cluster the principle characteristics were determined using factor analysis. Obtained results showed that the groundwater quality in this region is critical. Detection level of nitrate ranged from 20 to 137 mg l, demonstrated a 83% of the 1 observations exceeding the critical level of 50 mg l. Further deterioration of the groundwater quality with 1 agricultural development in this area can be expected if no mitigation strategies are developed.