Antibacterial and antioxidant chitosan-xylan/cellulose nanowhiskers (CNW) nanocomposite films were successfully prepared using CNW as nanofillers. The structure and morphology of the nanocomposite films were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). The optical transmittance, thermal stability, mechanical property, and swelling property of the nanocomposite films were also evaluated. These results revealed the microstructure of the films and confirmed the good miscibility between chitosan-xylan and CNW. The improvements of tensile strength and elongation at break of the nanocomposite films confirmed the reinforcement effects of CNW. Moreover, the inhibitory effects against S. aureus and E. coli and the ABTS+ scavenging activity indicated antibacterial and antioxidant functions of the nanocomposite films. In this work, the prepared chitosan-xylan/CNW nanocomposite films, combined the antibacterial property of chitosan, the antioxidant property of xylan, and good mechanical property of CNW, could be potentially applied in food and health-related areas.