Abstract: The use of nanosilver particles in medicine, due to its antibacterial and antifungal characteristics, dates back hundreds of years. However, several studies indicate that besides the antibacterial characteristics, these nanoparticles have high toxic effects on mammalian cells. For this study, 32 Wistar male rats were obtained. After 2 weeks of accommodation, they were randomly divided into groups; three nanosilver-treated rat groups and one Control Group (CG). The three treated groups were exposed to 5 cc of solution containing 5, 10 and 100 ppm nanosilver(Ag) (group 1, 2 and 3, respectively) via IP injection for 7 successive days. The control group was treated with 5 cc of normal saline solution with the same procedure. This study was performed to investigate the effect of different nanosilver concentrations on biochemical parameters such as Serum Glutamic Oxaloacetic Transaminase (SGOT) and Serum Glutamic-pyruvic Transaminase (SGPT) at various time points (2, 7 and 14 days). After 14 days, the tissue of liver and lung were collected and investigated. There was no significant difference between SGPT and SGOT liver enzymes in different groups (p>0.005). However, the amount of SGOT enzyme had increased in the treatment groups compared to the control group but this difference was not significant. Liver histological findings in this study showed no pathological changes except the decrease in acidophilic property in treatment group 1; reduction in acidophilic property, hepatocyte hypertrophy, full sinusoids fading and hyperemia of the central veins in treatment group 2 and reduction of acidophilic properties, hepatocyte hypertrophy, fading and thinning of sinusoids and slightly enlarged central veins in treatment group 3. The histological findings of the lung in the group receiving a 10 ppm concentration of nanosilver were complete destruction of air sacs and bronchioles and disfiguring of the lung tissues from their normal form. Moreover, in the group receiving a concentration of 100 ppm they were sever and clear hyperemia, disfiguring of the air sacs from their normal form, abnormal condition of the bronchioles, vessel rupture and blood leakage to the bronchioles and air sacs. The histological findings in the group receiving a concentration of 300 ppm were complete destruction of air sacs and bronchioles and obvious hyperemia in the tissue (which indicates the impact of nanoparticles in this tissue, deformity in some places were so much that it was not possible to identify lung tissue). According to the findings it can be concluded that the nanosilver particles, which were used in the form of solution in citrate stabilizer, with spherical shape and 10 nm in size caused complete destruction of lung tissue and partially destroyed liver tissue.