The purpose of this study is comparison of carob with placebo in the treatment of male infertility. This study was performed as a clinical trial with two-group pretest-posttest design. Each group consisted of 30 members. The first group received 1.5 grams of carob per day, and the second group received placebo treatments. Treatment lasted for 12 weeks. Semen analysis as well as testosterone, prolactin, (LH), (FSH) and (TSH) were performed before and after drug treatment in two groups. Sexual function was assessed in the groups in two stages before and after the intervention using the standard International Index of Erectile Function. P-value less than 0.05 was considered statistically significant. Statistical analysis of data was performed using SPSS 16. The participants' mean age was 34.83 ±6.22 in the placebo and 33.67 ±5.82 years in the Carob group. The results showed in the carob group compared to the placebo group, the rate of normal sperm counts increased by 17% and also the normal level of testosterone was 40% higher than the abnormal levels of the placebo group and these differences were statistically significant (P <0.05). And in most areas of sexual function, the mean scores after the intervention were higher than before (P> 0.05). It is recommended to use carob supplements to improve spermogram parameters and male sex hormones.