The genotoxic effects of quinalphos (QP) were evaluated in the erythrocytes of Cyprinus carpio using the comet, micronucleus, and nuclear abnormality assays. The 96 h LC50 value of quinalphos, estimated by static renewal system, was 10.9 μL/L. On the basis of the LC50 value, two sublethal concentrations (1.09 and 2.18 μL/L) of the compound were used together with cyclophosphamide (5 mg/L) as the positive control. The fish were exposed for 35 d, and sampling was done at the end of 7, 14, 21, 28, and 35 d. Our results reveal a significant dose-dependent increase in the frequencies of DNA strand breaks, micronucleus, and nuclear abnormalities. Similar responses were also observed in fish exposed to the positive genotoxin cyclophosphamide. The collective findings demonstrated that quinalphos exerts a genotoxic effect on C . carpio. The results further confirmed that the comet, micronucleus, and nuclear abnormality assays are useful tools in determining the potential genotoxicity of pesticides towards aquatic organisms.