For assessment of water quality in Gharasou River, located in the Northwest of Iran, multivariate statistical analysis was used. During the period of one year, 18 physical, chemical and microbiological parameters were sampled in 11 sampling stations. The measured data were analyzed by a multivariate statistical approach, Cluster Analysis (CA). Based on CA analysis the stations were divided to three groups of highly polluted (HP), moderately polluted (MP), and less polluted (LP) stations. The results of the study revealed that multivariate statistical techniques are an effective statistical method for water quality assessment, identification of pollution sources/factors in water quality for effective water quality management. As Extracted clustered information can be used in reducing the number of sampling sites on the River without missing much information.