The protective effect of vitamin E (VE, α-tocopherol) on methyl methanesulfonate (MMS)-induced teratozoospermia was investigated in adult rats. Rats (n=6 per group) were divided into three groups: i) Control group, treated with distilled water from days 1 to 5; ii) the MMS group, treated with MMS at a dose of 40 mg·kg(-1) from days 1‑5; or iii) the VE+MMS group, treated with MMS at a dose of 40 mg·kg(-1) from days 1‑5, followed by VE at a dose of 150 mg·kg(-1) from day 6 for 6 weeks. Sperm count, motility and morphology were examined following treatment with VE. The serum testosterone level and antioxidant enzyme activity were measured, and the localization of Vasa, promyelocytic leukemia zinc finger protein (Plzf) and synaptonemal complex protein 3 (Scp3) were also examined. MMS treatment decreased sperm count and motility, and the levels of immunoreactive serum testosterone and endogenous antioxidants. In addition, MMS increased the percentage of abnormal sperm and the levels of free radicals. After MMS and VE treatment, sperm count and motility were significantly higher in rats from the VE+MMS group than in the MMS group. In addition, the serum testosterone concentration, as well as the levels of Vasa and free radicals and the percentage of abnormal sperm, decreased. The results indicated that VE has protective effects against MMS-induced teratozoospermia in adult rats.