Prochilodus lineatus, a fish, was exposed to sublethal concentrations of cypermethrin: 0.075, 0.150, and 0.300 μg L(-1) and a control group (without cypermethrin) for 96 h. Five specimens were exposed in each concentration for triplicate (n = 60). Hepatic biochemical values and behavioral changes were studied. The results revealed a significantly higher level of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in hepatic tissue at different concentrations of cypermethrin tested compared to control (p < 0.05). A decrease in total protein was observed in exposed groups but not significantly (p > 0.05). This study provides information to know toxic mechanisms of cypermethrin on hepatic enzymes of P. lineatus that are poorly understood.