Background: Endometriosis is a gynecological disorder characterized by the growth of endometrial tissue outside the uterine cavity that is associated with chronic pelvic pain, subfertility and 1-3% increased risk of ovarian cancer. The purpose of the study was to investigate the effect of broccoli extract (BE) alone and in combination with soy isoflavones (SI) on endometrial implants in female rat. Method: In this study, endometriosis was induced surgically in 40 mature female rats. The rats were divided into 5 groups that were treated by oral gavage for 6 weeks with 0.5 ml of saline 0.9%/day (control group), BE (3000 mg/kg/day), SI (50mg/kg/day), BE/soy isoflavones (BE 3000 mg/kg/day + soy isoflavones 50mg/kg/day) and diphereline as a standard medication (3 mg/kg) intramuscularly. At the end of treatments, the volume and histopathology of the endometrial implants were compared among the 5 groups. The serum levels of oxidative parameters including Superoxide dismutase (SOD), Malondialdehyde (MDA) and tumor necrosis factor alpha (TNF-α) were also compared between the groups. Results: The volume of the implants significantly decreased in diphereline group (p = 0.002). The histopathological grade of endometrial implants in BE/SI and diphereline group were significantly decreased compared to the control group (p = 0.001). The serum levels of SOD in BE group were enhanced significantly in comparison to the control group (p = 0.034). Conclusion: BE in combination with SI decreased the growth and histopathologic grades of transplanted endometrial implants. These herbal compounds may have the potential to be used as an alternative medication for the treatment of endometriosis