Diabetes in a long period can damage the testicular tissue and impair the male fertility potential. Recently, different herbal treatments have been used for the prevention of type I diabetes and its pathological effects. Methanolic extract of Equisetum arvense has anti-oxidant and hypoglycemic properties. Thus, the current study aimed to evaluate the protective effects of Equisetum arvense methanolic extract (EE) on diabetes-induced detrimental effects in mice testicular tissue. Thirty-two adult male mice were randomly divided into four groups including control-sham, diabetic (induced by streptozotocin, 50.00 mg kg^-1 for five days), diabetic + EE 250 (250 mg kg^-1) and diabetic + EE 500 (500 mg kg^-1). After 45 days, all animals were euthanized and their testicles were dissected out and undergone histological analyses. Moreover, the serum level of testosterone was evaluated. Analyses showed that seminiferous tubules diameter, Leydig cells number per mm² of the connective tissue, Sertoli cells number per tubule, serum level of testosterone and percentage of seminiferous tubules with positive tubular differentiation, repopulation and spermiogenesis indices were significantly decreased in the diabetic group in comparison with control-sham group. The administration of EE in test groups significantly decreased the adverse effects of diabetes (especially 500 mg kg^-1). The results of this study revealed that diabetes disturbs spermatogenesis and spermiogenesis processes in mice. Meanwhile, the EE prevents diabetes-induced damages in mice testicular tissue, which may be associated with its hypoglycemic and antioxidative activities.