In this paper, unzipped multiwalled carbon nanotube oxides (UMCNOs), obtained by oxidation unzipping multiwalled carbon nanotubes (MWNTs) were used as novel nanofillers for mechanical reinforcement of chitosan (CS) matrix. The UMCNOs/CS nanocomposite films with different amounts of UMCNOs were fabricated by solution-casting the mixtures of UMCNOs and CS acetic acid aqueous dispersions. The structures and mechanical properties of the nanocomposite films were characterized by XRD, FT-IR, SEM, and tensile tests. The results demonstrated that UMCNOs could be homogeneously dispersed throughout the chitosan matrix. Compared to neat chitosan, the UMCNOs/CS nanocomposite films showed similar to 105.9% increase in tensile strength from 69.3 to 142.7 MPa, and similar to 165.3% increase in Young's modulus from 2.6 to 6.9 Gpa with the incorporation of only 0.2 wt% of UMCNOs into the chitosan matrix. (C) 2011 Elsevier Ltd. All rights reserved.