BACKGROUND: This study was initiated to improve our understanding  of the health and environmental impact of silver nanoparticles (Ag-np). OBJECTIVES: The purpose of the study is application and direct effects of silver nanoparticles on Zebra fish (Danio rerio). METHODS: After characterizing the AgNPs using TEM, EDX, UV-Vis Spectroscopy, XRF and SEM methods, their effects on some vital tissues have been tested successfully in vitro. In this study, 540 fish (2±0.05 g) were randomly divided into 9 groups in triplicate for acute tests (0,10, 50, 100, 200, 400, 600, 800 and 1000 mg/kgfood). After short term (96h), chronic toxicity tests were evaluated using under lethal concentration (100, 400, 600 and 800 mg/kgfood) fed with experimental diet for 8 weeks. Fish in groups 1 to 4 were fed by food supplemented with 100, 400, 600 and 800 mg/kg food, respectively. Group 5 was fed with basal food without supplementation. After histopathology, heavy metals were measured by spectrum photometry reveal. RESULTS: According to the results of acute tests, the 96h LC50 values in 24, 48, 72 and 96h were 804.601, 486.637, 323.696 and 195.208 mg/kgfood AgNPs for the Zebra fishes respectively. According to the results of chronic toxicity tests, fed via oral administration of AgNPs produced significant histopathological effects. Also, the most important histopathological effects of AgNPs were observed in the liver (vasculature and exposure, degeneration of some hepatocytes), intestine (increase in the submucosa layer, narrowing of the intestinal lumen  and reduced intestinal absorption), gills (clubbing of gill secondary lamaleas, hyperplasia, hyperemia and shortening of the primary lamaleas gills) and kidney (degeneration, high increase in interstitial cells and dilatation of Bowman’s space of glomeruli), respectively. The greatest bioaccumulation of silver occurred in the liver, gills and muscle of fish respectively (p<0.05). CONCLUSIONS: The release of untreated nanoparticle waste to the environment should be restricted for the well-being of human and aquatic species.