Deltamethrin (DLM) is α-cyano (type II) synthetic pyrethroid. DLM exposure leads to strong neurotoxic effects and a number of complex toxicological syndromes. The current study assessed DLM mediated oxidative stress, behavioral, hematological, histopathological, and biochemical toxic effects on silver carp (Hypophthalmichthys molitrix). Exposure to an acute concentration (2 μg/L) of DLM resulted in different behavioral inconsistencies and a time-dependent significant (P < 0.05) change in the hematology and serum biochemistry of silver carp. A significant (P < 0.05) increase in the activities of reactive oxygen species, lipid peroxidation, and antioxidant enzymes whereas a significant decrease in total protein contents in the liver, gills, brain, and muscle tissues were observed. DLM exposure increased the activities of metabolic enzymes in the gills, muscles, and liver of silver carp. A significant (P < 0.05) increase in DNA damage in peripheral blood erythrocytes was evident. DLM exposure led to a time-dependent significant (P < 0.05) increase in the whole-body cortisol and blood glucose level, while a significant decrease in acetylcholine esterase activity in the brain, liver, and muscle tissues. Different histopathological changes in the liver, gills, brain, and intestine were observed, however, no significant change in the gross anatomy and morphometric parameters of the fish was observed. The current study provides valuable information for devising better strategies regarding environmental management, chemicals' risk assessment, biodiversity conservation, and monitoring of the aquatic organisms. DLM was concluded to be highly toxic to fish. The extensive use of DLM should be prohibited or allowed under strict environmental laws; otherwise, it might lead to the extermination of the susceptible wildlife, such as commercially very valuable but nearly threatened silver carp.