Background: Active immunization against GnRH decreases the secretion of gonadotropins and causes cessation of gonadal function, thereby, inducing infertility. Based on the immunoenhancing activity of Kamdhenu ark (distilled cow urine), this study was performed to evaluate its effects on the gonadosomatic indices (GSI) and sperm parameters in male mice receiving a GnRH contraceptive vaccine. Methods: Sixty adult male mice of Parke’s strain were divided into three groups of twenty. Group I served as the controls, while group II was immunized by GnRH-BSA conjugate (50/0.2/35 µg/ml/g BW) by four intraperitoneal injections at different intervals on days 1, 30, 60 and 90. However, group III was supplemented daily by oral Kamdhenu ark (100 ppm) along with GnRH-BSA immunizations. The animals were sacrificed after 30, 60, 90 and 120 days and their testis and epididymis were dissected out weighed and semen analysis was performed. Results: GSI values, sperm motility, sperm count and sperm morphology in male Mus musculus were decreased significantly in all the experimental groups as compared to the control group (p < 0.01). Kamdhenu ark significantly enhanced the effect of GnRH vaccine on the aforesaid parameters especially in 90 and 120 days treated groups (p < 0.05). Conclusion: The changes witnessed in sperm parameters suggested that the GnRH-BSA immunization suppressed the activities of gonadotropins and testosterone directly through hypothalamo-hypophysial-gonadal axis and indirectly by acting on the testes which may modulate the sperm morphology, sperm count and motility. However, Kamdhenu ark seems to have enhanced these effects because of its immunemodulatory properties too.