Objectives: We evaluated role of tribulus terristrus in male with unexplained infertility and its effect on serum testosterone and semen parameters. Patients and Methods: Thirty randomized male patients presenting to Andrology out-patient clinic complaining of idiopathic infertility. Interventions: They were given tribulus terristrus (750 mg) in 3 divided doses for 3 months. Main outcome measures: Study of the effect of tribulus terristris had been monitored for its effect on serum testosterone (Total & Free) & LH, as well as it's Impact on semen parameters for those patients. Results: There was no statistically significant difference in the level of testosterone (Total & Free) & LH or semen parameters (sperm concentration or motility or abnormal forms) before & after treatment was observed. Also, There was no statistically significant correlations were observed between testosterone (free & Total) & LH and the semen parameters before and after treatment. Conclusion: It was concluded that Tribulus terrestris was ineffective in the treatment of idiopathic male infertility