© 2020 Japan Pediatric SocietyBackground: In this study, we assessed thiol/disulfide homeostasis (TDH) parameters and ischemia-modified albumin (IMA) levels in children with irritable bowel syndrome (IBS) compared with healthy children. Methods: Fifty-six children with IBS and 53 healthy children were included in the study after assessment of inclusion and exclusion criteria. Plasma thiol/disulfide and IMA levels were compared between children with and without IBS. Results: The mean values of native thiol, total thiol, and disulfide were 343.779 (Formula presented.) 138.654 μmol/L, 365.398 ± 140.148 μmol/L, and 23.190 ± 4.978 μmol/L, respectively, in the IBS group and 409.908 ± 69.288 μmol/L, 433.481 ± 76.891 μmol/L, and 20.090 ± 4.252 μmol/L, respectively, in the control group. Native thiol and total thiol values were significantly reduced in the IBS group compared with the control group. The mean IMA values were 0.835 ± 0.083 (g/L) and 0.778 ± 0.072 in the IBS and control groups, respectively. The IMA value was significantly increased in the IBS group. Conclusion: Impaired thiol/disulfide homeostasis and increased IMA levels can be considered etiological factors in children with IBS.