Background: Endometriosis is a common gynecological disease in which oxidative stress is a potential factor. Caffeine and caffeic acid are present in various foods and beverages with anti-oxidant, anti-inflammatory, and anti-carcinogenic properties. In this study, we aimed to investigate the ameliorative effects of caffeine, caffeic acid, and caffeine+caffeic acid treatments on oxidative stress in ectopic endometrial cells taken from patients and eutopic ones from women without endometriosis.Methods: In this experimental study, eutopic and ectopic endometrial cells were obtained from biopsies of women free of disease (n=10) and patients with endometriosis (n=10) who referred to Shiraz reference hospitals (2017-2018). Both eutopic and ectopic endometrial cells were divided into four groups: Treated with caffeine, with caffeic acid, with caffeine+caffeic acid, and the control. Also, antioxidant enzyme activities and the levels of glutathione (GSH) and malondialdehyde (MDA) were determined in each group. The data were analyzed using independent sample t test and one-way ANOVA followed by Tukey post-hoc test.Results: Caffeic acid, but not caffeine treatment demonstrated a decrease in MDA level (P<0.001) as well as an increase in GSH level (P<0.001) and antioxidant enzyme activities in ectopic endometrial cells. Also, the treatment of the cells with caffeine+caffeic acid caused similar effects as those ectopic cells treated with caffeic acid. Conclusion: According to the findings of the present study, caffeic acid reduced oxidative stress which may alleviate the complications associated with endometriosis. However, more investigations are needed for evaluating the efficiency and safety of caffeic acid.