The present study aims to evaluate the role of follicular fluid (FF) and serum (s) total oxidant status (TOS), total antioxidant status (TAS) and oxidative stress index (OSI) on the etiopathogenesis of unexplained infertility (UI) and intracytoplasmic sperm injection-embryo transfer (ICSI-ET) success. Twenty UI patients and 20 controls with male factor undergoing an ICSI-ET cycle were recruited. FF samples aspirated from mature follicles and blood samples collected just before the oocyte retrieval were stored until analysis. Embriyo quality and implantation, clinical pregnancy and living birth rates were evaluated. FF-TOS and FF-OSI of the UI patients were higher than the control group. s-TOS and s-OSI were significantly increased in the UI group compared to the control group. However, only s-TOS was positively associated with UI diagnosis after age-adjustment. FF-OSI was negatively associated with embryo quality in the UI group (but not in the whole group) after age-adjustment. No significant effect of TAS, TOS, and OSI on implantation, clinical pregnancy and live birth rate was observed. In conclusion, especially s-TOS can have a partial role in the etiopathogenesis of UI. High FF-OSI can decrease the quality of embryo in patients with UI.Impact statement What is already known? Total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI), which is the ratio of TOS to TAS, provide a broad overview of redox status. What do the results of this study add? An elevated serum TOS (s-TOS) was associated with UI after age-adjustment. Follicular fluid OSI (FF-OSI) was negatively associated with embryo quality and embryo score in the UI group (but not in the whole group) after age-adjustment. No significant effect of TAS, TOS, and OSI was observed on implantation, clinical pregnancy, and live birth rate. What are the implications of these findings for clinical practice and/or further research? Evaluation of FF-OSI in women with unexplained infertility can be considered to predict embryo quality. Further studies that evaluate antioxidant agents to decrease oxidative stress in UI and its' clinical implications are warranted.