Aquatic environments are hospitalized for contaminants and most fish life is in contact with the water. Due to its resistance, anatomical and physiological similarities to other carp fish, goldfish was chosen in the present study as biological model in order to study the effect of silver nanoparticles on hematological parameters of carps. For the biochemical and hematological tests of the groups under investigation, nine fish were randomly selected from each treatment and were separately exposed to effective concentrations of nano-silver in 0.1, 0.5, 1 and 5 ppm. Measured indices included total number of white blood cells (leukocytes), lymphocytes, neutrophils, eosinophil, total number of red blood cells (erythrocytes), hemoglobin content, hematocrit level, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) and serum glucoses. Results showed that different concentrations of nano silver had significant effect on blood erythrocyte factors but not on leukocyte parameters. This may be due to the resistance of goldfish in comparison with the other fish species.