Abstract Chlorpyrifos (CPF) can induce ovarian damage and reproductive dysfunction through oxidative stress mechanisms. These can be reversed by antioxidants such as Epigallocatechin-3-gallate (EGCG) in green tea. This study aimed to investigate the toxicity effects of CPF on rat ovaries and the effectiveness of EGCG to protect against these effects. Fifty adult female albino rats were randomly assigned to five equal groups; negative and positive control groups, EGCG-treated group, CPF treated group and CPF+EGCG-treated group. After four weeks the rat body weight and relative ovarian weight were estimated, and blood samples were collected to assess reproductive hormones (RHs) levels. Evaluation of ovarian oxidative stress indicators malondialdhyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), reduced glutathione (GSH) and catalase (CAT) was performed. Ovarian sections were prepared and examined using the hematoxylin and eosin stain, proliferating cell nuclear antigen, and morphometric study to assess histopathologic changes. CPF treated rats had significant lower body weight and relative ovarian weight compared to controls (P<0.001) and those treated with CPF+EGCG (P<0.001). CPF induced significant reduction in RHs levels and ovarian SOD, GSH and CAT activities when given alone, which were improved by the combined administration of CPF and EGCG. The levels of ovarian MDA and NO were significantly higher in CPF-treated rats than controls and rats treated with CPF+EGCG. The cellular proliferation in ovarian Graafian follicles was significantly suppressed in CPF-treated animals. Hence CPF can induce oxidative damage in rat ovaries, EGCG, a natural potent antioxidant, can be useful against the CPF toxicity effects in ovaries.