Background and AimsFatty liver increases oxidative stress and may trigger antioxidant mechanisms. We aimed to compare the levels of vitamin D, which has antioxidant properties, as well as total oxidant status (TOS), total antioxidant status (TAS), and catalase between patients with nonalcoholic fatty liver (NAFL) and the control group.MethodsWe compared vitamin D, TOS, TAS, catalase levels, and other biochemical parameters between pediatric patients with ultrasonographically detected NAFL and an age-matched healthy control group.ResultsNAFL patients had a significantly lower vitamin D level (p < 0.001). The patient group also had significantly greater height, weight, body mass index (BMI) Z score, parathyroid hormone, triglyceride, glucose, antioxidant (TAS and catalase), and TOS levels compared to the controls (p ≥ 0.001). There was no significant difference between the obese and non-obese NAFL patients with respect to TAS, TOS, catalase levels, and other biochemical parameters (p < 0.05). There was a positive correlation between height, weight, BMI Z score, and hepatosteatosis grade, and TAS, TOS, and catalase levels, and a negative correlation with vitamin D level. We also found a negative correlation between vitamin D level and TOS and catalase level.ConclusionsOur study revealed lower levels of vitamin D and higher levels of oxidant-antioxidants including TOS, TAS, and catalase in patients with NAFL.