The increasing use of heavy metals in industry in the modern world unfavorably affects the aquatic environment. Acute toxicity of nickel to the fresh water fish carassius auratus was determined using Probite analyze, Fish were exposed to selected concentration of nickel and the mortality data were determined after 24, 48, 72 and 96 hours. LC50 values for 24,48,72 and 96 hours were calculated with the 95% fiducially limits. The 24,48,72 and 96 hours LC50 values of nickel to the fish were 161.78 ± 3.05, 130.58 ± 2.32, 110.19 ± 1.57, 100.39 ± 0.54 ppm respectively. White blood cell (WBC) count, hemoglobin (Hb) and hematocrit (Hct) level were significantly reduced at experimental concentrations (p<0.05). Red blood cell (RBC) count, mean corpuscular hemoglobin (MCH), cortisol and glucose levels in nickel treated groups were significantly higher than the controlled group at experimental periods (p<0.05) but significant differences were not found in mean corpuscular hemoglobin concentration (MCHC) and mean corpuscular volume (MCV) (p>0.05). In summary, nickel intoxication resulted indicated that hematological and biochemical parameters can be used as an indicator of nickel related stress in fish on exposure to elevated nickel status.