Hormonal disorders, oxidative stress, and inflammation in ovarian tissue cause ovulation failure in women with polycystic ovary syndrome. Considering the antioxidant properties of gallic acid (GA), the aim of this study was to investigate the effect of GA on pro-inflammatory cytokines, antioxidant enzyme activity, and DNA oxidative damage of ovarian tissue in a rat model of estradiol-induced polycystic ovary (PCO). In this experimental study, 32 female Wistar rats were divided into four groups. These included control (saline solution, orally), PCO+saline (estradiol valerate + saline solution, orally), PCO+GA50, and PCO+GA100 (estradiol valerate +50 and 100 mg/kg gallic acid, orally), respectively. The PCO model was induced by a single intramuscular injection of estradiol valerate (EV, 4 mg/kg). Twenty-four days after PCO modeling, tissue concentration of tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) and also the activity level of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), malondialdehyde (MDA), and 8-oxo-2′-deoxyguanosine (8-OHdG) in ovarian tissue were measured through ELISA technique. Compared with the PCO+saline, in the GA-treated group, the concentration of TNF-α, IL-1β, and IL-6 in a dose-dependent manner significantly decreased (p > 0.05). In addition, the activity level of SOD, CAT, and GPX enzymes significantly increased (p 0.05) in a dose-dependent manner. GA is an anti-inflammatory and an antioxidant polyphenol which reduces the concentration of inflammatory cytokines, oxidative stress, lipid peroxidation, and DNA oxidative damage of ovarian tissue in a rat’s model of PCO.