Objective: Curcumin (diferuloylmethane) is a a compound isolated from turmeric with biological activities, including antifertility. Curcumin inhibits COX-2 expression in granulosa cells of ovarian follicles and disrupts vascular endothelial growth factor (VEGF) derived angiogenesis in the endometrium, reducing endometrial receptivity. The purpose of this study was to examine the effects of curcumin on COX-2 and VEGF expression in endometrium of fertile women. Methods: A prospective double-blind placebo-controlled clinical trial was conducted in a group of fertile women with regular menstrual cycles, aged between 20-30 y, married, and with children. Subjects were divided into a group receiving daily 800 mg encapsulated curcumin. Curcumin orally for ten days, starting on the third day of the first menstrual day, and a control group. Endometrial biopsy was performed using a microcuret and immunohistochemistry was used to assess VEGF and COX-2 expression. The results were analysed using an independent sample t-test. Results: In the curcumin-treated group, VEGF expression was significantly lower than the control group (p<0.05), and COX-2 expression was higher but not significantly so (p>0.05). Conclusion: The curcumin causes VEGF expression in endometrium is lower and negatively affects the growth of endometrial stromal cells.