Heavy metals contaminations are considered as one of the serious threats in natural habitats due to their toxicity, persistence and bioaccumulation characteristics. Environmental monitoring is an appropriate approach to measure the concentration of heavy metals and their bioavailability in biological systems for implementation of remediation strategies. Change in heavy metal concentration potentially affect bird populations that are at the higher levels of food chains in an ecosystem. Birds are sensitive to toxic substances; therefore birds are often regarded as bioindicators of heavy metal pollution. In this study, the concentrations of heavy metals such as zinc, lead and cadmium were measured in Beshar River sediments, Spirogyra algae, Levantine scraper fish, and some birds (i.e. Pied Kingfisher, Common Snipe, Chukar, Osprey, Purple Heron, and Hooded Crow) in Dena Biosphere Reserve. In addition, the bioaccumulation of the heavy metals in three birds’ food chains was studied. Our results showed that the concentration of Lead in the sediments samples was lower than freshwater Standards, however the concentration of Zinc and Cadmium was higher than the standards. This results revealed Zinc and Cadmium contamination in the sediments of Beshar river. Regarding Spirogyra algae, our results showed a high level of contamination by all the three heavy metals in all the sampling points, where the highest and lowest concentrations were observed in sampling point No. 2 (where Yasuj city wastewater releases to Beshar River), and in sampling point No. 5 (the lowest border of the Province). For Levantine scraper, the concentration of all three studied heavy metals were exceeded the standards and showed a high-level contamination of heavy metals in fishes. The concentration of the heavy metals (i.e. Zn, Pb, Cd) in birds was measured in four birds tissues including liver, kidney, feather and muscle, in six species of birds (i.e. Chukar, Hooded Crow, Common Snipe, pied kingfishers, Osprey and Purple Heron). The results showed a significant difference among the concentration of all three metals in all tissues where the highest level observed in feather and the lowest level in breast muscle, respectively. According to the results, the kidney and feather might be the better tissues for monitoring of lead and zinc, and Cadm ium, respectively. Moreover, the level of bioaccumulation of cadmium and lead in aquatic bird tissues was higher than those in terrestrial birds tissues, however we did not find significant differences in Zinc concentration among aquatic and terrestrial birds tissues. By comparing the concentration of studied heavy metals in birds tissues with the Standards, it has been seen that concentration of Cadmium in most sample tissues is lower than Standard. However, those concentrations in kidney of Common Snipe exceeded the Standards, and for the other tissue samples, there was not any level of contamination to Cadmium observed. Moreover, the results showed that all tissue samples have contaminated by lead; about the concentration of Cadmium, all tissue sapmles, except the breast muscles of Chukar, Common Snipe and Pied Kingfisher, are exceeded the Standards. Our results revealed that heavy metal bioaccumulation accrued in part of the bird’s food chain in the study area. Keywords : Heavy metals, Dena Biosphere Reserve, Bashar River, Sediment, Spirogyra Algae, Levantine scraper fish, Birds, Food chain.