To evaluate the effects of dietary high molybdenum (HMo) and low copper (LCu) concentrations on reproductive toxicity of male mice, 80 mice were divided into 4 groups of 20. These groups were fed with the following: (I) normal control (NC) diet (NC group); (2) NC and HMo diets (HMo group); (3) LCu diet (LCu group); and (4) HMo and LCu diets (HMoLCu group). On the 50th and 100th day, superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) were analyzed to determine oxidative stress states. Morphological changes in testicular tissue were evaluated with hematoxylin and eosin staining and ultrastructural changes were monitored by transmission electron microscopy. The results showed that administration of HMo, LCu, and HMoLCu not only decreased sperm density and motility but also increased the rate of teratosperm occurrence. A significant increase in MDA content and a decrease in SOD, GSH-Px, and T-AOC contents were observed in LCu, HMo, and HMoLCu groups. Testicular tissues and cells of mice were damaged by HMo and the damages were more serious in the case of Cu deficiency. Exposure to HMo adversely affected the reproductive system of male mice, and dietary LCu plays key roles in HMo-induced reproductive toxicity.