Pesticides not only brought great economic benefits but also cause serious ecological harms like non-target toxicity of organism. Synthetic pyrethroid (deltamethrine) is widely used due to its less toxicity and easy degradation in soil.In this study,fresh water fish Hypophthalmicthyes molitrix were exposed to sub lethal concentrations of deltamethrine. Fish were divided into 4 groups and each group contains six fish. Experimental groups viz. A, B and C were exposed to 25, 50 and 75% of LC50, respectively for four days. Blood samples for biochemical analysis (blood glucose, cholesterol and total protein) and gills for histology were taken after 96 hrs. After acute exposure to pesticide, significant changes were observed in serum biochemistry and histology. Serum glucose and cholesterol were increased while total protein was decreased. Histopathological result reveled that gills of experimental fish was damage severely resulting Necrosis, Damaged nuclei , rupturing of epithelial cells, Mucous cells and severe lamellar fusion. It was concluded that, deltamethrine is highly toxic for non-target aquatic organisms like silver carp (Hypophthalmicthyes molitrix).