This study investigated the effect of quercetin on changes in testes due to arsenic exposure. Twenty-seven male rats were divided into three groups: control (10 ml kg-1 day-1 saline), arsenic (10 mg kg-1 day-1 sodium arsenite) and arsenic + quercetin (arsenic + 50 mg kg-1 day-1 quercetin). The rats were sacrificed at the end of 15-day experiment. There was no difference between control group and arsenic group in body weight gain, testicular weight and serum total testosterone level. Quercetin treatment did not cause a significant difference in these parameters. In the arsenic group rats, we determined deterioration in the structure of seminiferous tubules, a decrease in the number of spermatogenic cells, an increase in the number of apoptotic cells, a decrease in the number of PCNA-positive cells, a decrease in SOD, CAT and GSH-Px activities, and an increase in the MDA level in testicular tissue. In all these changes, arsenic+quercetin group showed an improved compared to arsenic group. The amount of arsenic increased in the arsenic group was compared to the control group, and there was no difference between arsenic group and arsenic + quercetin group in the amount of arsenic. In conclusion, quercetin prevented arsenic-induced testicular damage with its anti-apoptotic and antioxidant effects.