Purpose: To study the effect of withaferin A on an experimentally-induced endometriosis (EM) model. Methods: Female Sprague-Dawley rats were induced EM by implantation of autologous endometrium. Rats in the treatment group were administered withaferin A orally for 30 days. A separate group of rats that was administered gestrinone (G TN) served as positive control. Results: Withaferin A treatment reduced the spherical volume of the ecto-uterine tissue was following five weeks after implantation. Histological analysis revealed regression of the lesions and restoration of normal architecture. Withaferin A effectively down-regulated the expressions and activities of matrix metalloproteinases (MMPs) 2 and 9 in the ectopic endometrium. The activities of MMPs-2 and 9 significantly (p<0.05) decreased from 1.79- and 1.65-fold to 1.08- and 1.1-fold, respectively. The EM-induced up-regulation of NF-kappa B/COX-2 signaling was down-regulated by withaferin A. The levels of Cox-2 decreased significantly (p < 0.05) from 198 % in EM control rats to 122.7 % in 150 mg withaferin A treated EM-induced rats. The increased levels of major inflammatory mediators nitric oxide (NO), TNF-alpha, Interleukins (IL) - IL-1 beta and IL-6, markedly (p < 0.05) were reduced by withaferin A treatment, when compared to EM control group. Conclusion: Withaferin A effectively suppresses the proliferation of lesions and modulates the immune responses-associated expressions of COX-2, NF-kappa B and matrix metalloproteinases (MMPs), viz, MMP-2 and MMP-9