Cadmium is known as an oxidative stress‐inducing factor. Silymarin extracted from Silybum marianum is regarded as a potent antioxidant. The present study investigated the preventing effects of silymarin on cadmium chloride‐induced toxicity in terms of testis histopathology and serum testosterone level as well as oxidative stress indicators in mice. In addition, the activities of antioxidant defence enzymes was evaluated. Adult male mice were divided into four groups (n = 6 in each group): (a) control; (b) cadmium chloride; (c) silymarin + cadmium chloride and (d) Silymarin. In this study, cadmium chloride significantly decreased the diameter and wall thickness of the seminiferous tubule, diameter of the spermatogonia nucleus and serum testosterone levels compared to the control group. Furthermore, in mice treated with this pollutant, a significant increase in malondialdehyde was observed while ferric reducing antioxidant power level, and the activity of catalase, superoxide dismutase and glutathione peroxidase were significantly reduced in the testis. In the silymarin + cadmium chloride group, silymarin could significantly reverse the toxic effects of cadmium chloride. The findings of this study showed that silymarin, as a potent antioxidant, can compensate the adverse effects of cadmium chloride on testis histopathology, testosterone level, oxidative stress indicators and antioxidant defence enzymes in mice.