Abstarct: Rivers are vital ecosystems and can be affected by both natural processes and human activities. This study focuses on Siahrood River, one of the main rivers flowing in alluvial basin of Qaemshahr and Juybaar in the Mazandaran province (Northern Iran). The aims of this investigation are the evaluation of water quality and contamination of bed sediments of the Siahrood River. For this purpose, 15 water and sediment samples along the river were collected. In addition to analyze heavy mextal content of the samples (by means of ICP-OES), some physicochemical properties of sediments such as clay content, pH and organic matter (OM) content were determined. Water quality parameters (major cation and anion concentrations, pH, EC, TDS, COD…) were also measured either insitu or in the laboratory. In order to interpret the water quality data, graphical methods (by depicting piper, Gibbs, Durov diagrams) and hydrochemical modeling (PHREEQC-Interactive software) were applied. The obtained geochemical results were also analyzed using multivariate statistical approaches (cluster analysis, principal component analysis and correlation analysis) and contamination status of the sediments were evaluated by calculating some geochemical indices such as enrichment factor (EF) and index of geoaccumulation (Igeo).The results showed that in upstream stations, sediments are coarse grain in texture, and towards the end of the river become fine grain. The organic matter content of the sediments ranged from 0.01% to 10.6%. Interpretation of water quality data reveals that main hydrochemical type of water samples is bicarbonate-calcic (except for two last sampling stations with sodic-chloric type). baxsed on calculation of Saturation Index (SI) and graphical interpretation of the water data, it was shown that dissolution (rock weathering) and mixing are the main processes controlling the chemistry of the river water. The obtained results of geochemical analyses on the sediments generally showed that lead and cadmium have elevated concentrations, higher than corresponding limits in the World Mean Sediments. Other mextals have relatively low concentrations in the sediments. The results of sequential extraction analysis (BCR technique) also denoted the cadmium and lead are mainly included in the first fraction suggesting their anthropogenic sources in the sediments. Other mextals (Ni and Cu, Cr, As and Ni) are associated with residual fraction of the sediments revealing their main geogenic source. Calculation of enrichment factor for the investigated mextals indicated that lead, arsenic and cadmium are comparatively enriched in the sediments, confirmed by calculated geoaccumaution indexes. From these results, it can be deduced that anthropogenic sources (e.g. urban runoff, municipal wastewater discharge, farming activities) along the river has influenced the heavy mextal content in the sediments. Finally, baxsed on results of water quality evaluation in terms of the water suitability for irrigation and drinking purposes, it was concluded that the river water is generally suitable for irrigation of farming lands but not good enough for drinking usages.