Objective: There is a balance among the free radical production and the antioxidant system suppressing the increase of reactive oxygen species in the body. If this balance is disturbed, then oxidative stress occurs. Free radicals caused by normal metabolism or pathological processes cause deterioration in the structure and functions of thiol-dependent enzymes and change in the thiol / disulfide balance in the cell environment. The aim of our study is to evaluate the dynamic thiol/ disulfide balance in children with acute malnutrition. Methods: The weight, weight Z score, height, height Z score and BMI of the patients in the study group were measured. 52 patients diagnosed with acute malnutrition according to Waterlow classification and 40 healthy children were included in the study. The thiol/ disulfide balance was measured in both groups by using the automatic method developed by Erel and Neselioğlu. Results: There was no statistically significant difference among patient and control group in terms of the average native thiol and total thiol levels. While it was found that the levels of disulfide, disulfide/native thiol and disulfide/total thiol were statistically significant in the patient group, the native thiol/total thiol ratio was found to be lower at a significant level. Conclusion: It was seen that thiol/ disulfide balance weakened in children with acute malnutrition and showed a shift towards disulfide.