The nanofiber sheets consisted of N-carboxyethyl chitosan (CECH) and poly(ethylene oxide) (PEO) were developed using an electrospinning process to prevent abdominal adhesions after surgical operations. Successful synthesis of CECH from chitosan was confirmed by FTIR. The morphology and biocompatibility of the nanofiber sheets were characterized using a scanning electron microscope and MIT assay. For in vivo assessments, CECH/PEO nanofiber sheets were implanted into the abdominal surgical site and the abdominal tissues were evaluated by histological examination. When the weight ratio of CECH to PEO was 3:3, the nanofiber showed the most similar thicicness between them. The MTT assay showed that the nanofibers had no significant toxicity toward NIH/3T3 cells at the high elution concentrations. The macroscopic and histological observation after 7 days of surgical process demonstrated that the CECH/ PEO nanofiber sheets prevented abdominal adhesion effectively. In conclusion, the CECH/PEO nanofiber sheets can be exploited to prevent postsurgical adhesions.