The aim of the present investigation was to determine the effect of heavy metal pollutants such as cadmium, chromium, nickel and lead in aquatic system on common carp (Cyprinus carpio L.) by using a set of biochemical parameters. The experimental group of fish was exposed to a sublethal concentration of 5 mg/L of combined (Cd+Pb+Cr+Ni) metal solution containing 1.25 mg/L of each metal ion (1/10th of LC 50/48 h) for a period of 32 days. The results indicated that the values of the hemoglobin were in the range of 55.30 ± 1.20 g/L to 74.55 ± 1.33 g/L (p<0.001) and the packed cell volume was in the range of 26.72 ± 0.26% to 30.68 ± 0.43% (p<0.01). Concentrations of red blood cells, blood glucose and total cholesterol were significantly elevated. The level of serum iron and copper was increased. The results showed the decreased activity of vitamin C during chronic exposure to toxic heavy metals, which indicates the presence of reactive oxygen species–induced peroxidation. The study suggested that the presence of toxic heavy metals in aquatic environment has strong influence on the hematological parameters in the fresh water fish common carp (Cyprinus carpio L.).