Argulosis is the sever problem in carp culture and its severity turns to be panic in case of unregulated treatment with ivermectin, when the post treatment mortality of the fish or subsequent slow growth becomes common. Therefore, present study was aimed to study the effect of acute ivermectin exposure (96 hr) of different concentration on antioxidative enzymes (catalase, superoxide dismutase, glutathione S-transferase), acetyl choline enzyme activity and hematological parameters like platelets, white blood cell (WBC), red blood cell (RBC), haemoglobin content, haematocrit (HCT), mean corpuscular haemoglobin concentration  (MCHC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and Nitro-blue tetrazolium (NBT) of a tropical freshwater fish, rohu  (Labeo rohita) fingerlings (5.5 g). The estimated LC50 value of 7.89 µg/L was found at 96 h of exposure by probit analysis. Activities of anti-oxidative enzymes, immune hematological profile and neurotransmitter activity were significantly altered (P < 0.05) in a dose dependent manner. The early gross sign like sluggishness and dark body were, followed by disorientation and imbalance in swimming, finally mortality during acute toxicity.