The current study was aimed to investigate the impact of nickel chloride exposure on the hematological parameters of grass carp (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix). Heavy metal pollution is a growing global concern affecting aquatic ecosystems and on inhabitants. In the present study the two fish species were exposed to nickel chloride for duration of 7 and 25 days. Result of Hematological profile, showed significant differences in responses between Grass carp and Silver carp. Grass carp exhibited substantial alterations in white blood cell count , hemoglobin (Hb), red blood cell count , hematocrit, mean corpuscular hemoglobin (MCH), red cell distribution width (RDW), mean platelet volume (MPV), platelet count (PLT), mean cell hemoglobin concentration (MCHC), and plateletcrit (PCT), indicating a strong immune response and physiological changes. In contrast, silver carp showed comparatively lower alterations during the seven-days of treatment in parameters: like mean corpuscular volume (MCV) was 136.7±0.90 fL, platelet distribution was (PDW) 15.83±0.64 %, while Grass carp showed alterations only in (PDW) 51.6±1.38%. For the period of 25 days, silver carp showed alterations in (MCV) and (MCH) 143.6±1.55fL and 28.70±0.11pg, and grass carp showed significant in (Hb) and (RDW-CV) 13.26±0.56gm/dL and 126.8±15.034%. Student‘t’ test was applied for the comparison of the data of control with the test samples. These species-specific responses highlight the importance of considering individual fish species' sensitivities which assessing the effects of environmental stressors like heavy metals.