SHIKHBAHAEI, F.; GHANBARI, A. & KESHTMAND, Z.Therapeutic effect of thymoquinone against methotrexate-induced damage on sperm parameters in mice. Int. J. Morphol., 36(2):519-522, 2018. SUMMARY:Methotrexate drug is commonly used to treat cancer; it is known to cause reproductive damage. Thymoquinone, as a natural component of herbs has many healthy benefits shown in researches. The present study aimed to investigate probable therapeutic effects of Thymoquinone against Methotrexate-induced damage on sperm parameters in mice. In this experimental study, 30 male mice (25-30 g) were divided into five groups of six in each group. The mice were received normal saline (control group), Methotrexate (20 mg/kg), Methotrexate (20 mg/kg) + Thymoquinone (2, 10 and 20 mg/kg) by intraperitoneal injection. On the day after the last injection, the sperm parameters including motility, viability and count of sperms were assessed. Data analysis was performed using one-way ANOVA followed by Tukey test. Methotrexate alone showed a significant reduction in sperm parameters compared to the control group (P=0.00). In groups treated with Methotrexate and Thymoquinone, sperm parameters (motility ,viability, count sperm) did not show any significant differences with control group (P=0.00). Thymoquinone, as a potent antioxidant, could compensate for the toxicity induced by Methotrexate. These medical trends may be useful for diminishing the side effects of Methotrexate on the male reproductive system.