Biodegradable poly(propylene carbonate, PPC) is a typical noncrystalline polymer from the copolymerization of carbon dioxide (CO2) with propylene oxide (PO). But it is easy to be degraded to propylene carbonate (PC) via backbiting route during heat process (above 170°C), which limits its application. This work reports the introduction of biodegradable nanocrystalline cellulose (NCC) which was exfoliated from microcrystalline cellulose (MCC) by acid hydrolysis into PPC, affording a biodegradable PPC/NCC nanocomposite with improved thermal decomposition temperatures (the initial decomposition temperature, T5wt% was up to 265°C). Impressively, the thermal decomposition of PPC to PC at 200°C within 4.0 h was dramatically inhibited by introducing NCC, which was evident by 1H NMR spectra. This could be attributed to the hydrogen bonding interaction between NCC and PPC. Moreover, the film of PPC/NCC nanocomposite had not deformed when it was heated at 110°C for 4 h. In application, such biodegradable nanocomposite is a promising disposable package material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39847.