Increasing industrial activities lead to entrance of different pollutants into the environment, especially water resources. Because of their persistency and non-biodegradation, metals can pose a threat to health of human and other organisms. Sediment, fish (lucioperca Stizostedion and Cyprinus carpio), and common reed (Phragmites australis) samples were collected from Sattarkhan dam for investigating their heavy metal concentrations. Dry and ashed sediment, fish, and common reed samples were digested using concentrated nitric acid and their heavy metals (As, Cu and Cd) concentrations were measured using an ICP-OES instrument. One-way ANOVA test was used to examine the difference among accumulation of various metals in plant, sediment and fish. Results showed that there were significant differences between metal concentrations in samples (P<0.001). No correlation was found among concentration of metals in sediment, plant and fish samples. Arsenic in sediments and arsenic and cadmium in fish tissues were higher than the international standards. Calculation of bioaccumulation factor (BAF) showed that Phragmites australis can accumulate these metals and may be used as their bioindicator in aquatic environments. Based on the high concentrations of metals which determined in sediment and fish samples, monitoring and controlling of heavy metals in this ecosystem are considered as a necessary approach.