With growing of Nano technology, it will inevitably lead to an increase in transforming of nanomaterials into the environment intentionally or accidentally. Aquatic enviroments are very vulnerable, act as locations for deposition and accumulation of the nanoparticles.The aim of this study was to assess the effects of silver nanoparticles and silver nitrate on some hematological and histopatological indices of Zayandehrud chub. For this purpose, 100 individuals of Zayandehrud chub with average weight of 26.4±1.3 g and length of 12.5±0.33 (Mean±SE) cm were captured from natural environment and transferred to the laboratory. Fish were randomly divided in to 5 experimental groups with different concentration in a complete randomly desing including: 1 µg/L silver nano particles (Ag), 1 µg/L silver nitrate (AgNO 3 ), 25 µg/L silver nano particles and 25 µg/L silver nitrate that each experimental groups with 15 fish specimens during 10 days were examined. At the end of the experiment, venesection of the fish caudal fins by using anesthesia was done and prevalent hematological indices were measured. Gill and liver tissue fixed in 10% formalin for histopatological studies at the last day of expousure. To assess the silver concentration in gill, liver, kidney, muscle and intestine tissues were determinated with atomic absorption spectrometry. The highest rate of hematocrit and hemoglobin was observed at doses of 25 µg/L silver nitrate which was significantly differenctes from the control group (p 0.05). Red blood cell count (RBC) decreased significantly compared to the control group at doses of 25 µgr/L silver nanoparticles (p 0.05) . Except the Mean corpuscular hemoglobin concentration (MCHC), other secondary hematological indices was observed significant differenctes from the control group (p 0.05). Hyperplasia, hemorrhage, edema and shortening of secondary lamella were the main gill histopatological sings and hemorrhage, focal necrosis, nuclei pyknosi and nuclei karyolysis were the main liver histopatologocal sings of Zayandehrud chub exposed to water born Ag and AgNO 3 . In addition, organ index was a significantly differentce for both gill and liver tissues at the dose rate of 25 µg/L AgNO 3 rather than other experimental groups. The highest rate of concentration of silver was observed in the liver tissue at the dose of 25 µg/L Silver nitrate which was significantly differentce from other treatments (p 0.05). Generally, in the Zayandehrud Chub tissues, the most and the least accumulation of silver was in the liver (2.48- 15.45 µg/g) and muscle tissues (0.19- 0.47 µg/g) respectively in all the experimental groups. Keywords: Ecotoxicology, Heavy metal, Accumulation, Freshwater fish .