Carboxymethylated chitosan (CMCS) has many beneficial effects, including anti-oxidant and anti-apoptotic actions. However, the mechanisms by which CMCS protect against oxidative stress induced damage to Schwann cells (SCs) remains unclear. The present study aimed to investigate the mechanism by which CMCS protects SCs against hydrogen peroxide (H2O2) induced damage. H2O2 was used to establish a model of oxidative stress injury in SCs to mimic the development of nerve injury in vitro. Different concentrations (50, 100 and 200 μg/ml) of CMCS were added to test whether CMCS was capable of protecting SCs from H2O2 induced damage. MTT, LDH release and Annexin V/FITC assays were then performed. Levels of reactive oxygen species were detected using a reactive oxygen species assay kit, the mitochondrial membrane potential (ΔΨm) of SCs was analyzed by rhodamine123 fluorescence staining, the synthesis of Bcl-2, Bax, cytochrome c and caspase-3 were analyzed by real-time PCR and Western blot analysis. The results showed that CMCS protected SCs from apoptosis, decreased LDH release and enhanced cell viability, also decreased reactive oxygen species levels and increased ΔΨm. Additional experiments demonstrated that CMCS could decrease protein expression of Bax, cytochrome c and caspase-3, while promote Bcl-2 protein expression induced by H2O2. Taken together, the finding of this study indicated that CMCS prevented H2O2-induced damage to SCs through the mitochondrial dependent pathway.