Aim: The main aim of this study was to investigate thiol/disulfide homeostasis associated with fetal growth restriction (FGR) and to evaluate whether alterations are predictive for adverse neonatal outcomes. Methods: 273 pregnant women (77 with FGR and 196 with normal fetal growth) were enrolled in this prospective case-control study. Results: Native thiol and total thiol were decreased in FGR compared to the control group (p < .001; p < .001). Decreased levels of maternal serum native and total thiol were significantly associated with adverse neonatal outcomes in FGR (OR: 0.983, 95% CI 0.976-0.991, p < .001; OR: 0.983, 95% CI 0.976-0.991, p < .001). Decreased maternal serum total thiol levels were the only significantly associated risk factor with adverse neonatal outcomes in FGR (OR: 0.981, 95% CI 0.963-1.000, p = .046). Conclusion: The decrease in the antioxidants of thiol/disulfide mechanism may be related to the development of both FGR and adverse neonatal outcome in FGR.