A study was conducted to evaluate the basic mechanical properties of a pure cellulose nanofiber (CNF) material in comparison with a commercial denture base material (polymethylmethacrylate [PMMA] acrylic resin). The working hypothesis was that CNFs have potential for use as denture base materials. Pure CNF specimens fabricated under various conditions were examined. The flexural strength (FS) and flexural modulus (FM) of the specimens were measured using the three-point bend-ing test, and the morphologies of the fractured surfaces were examined using scanning electron microscopy. Addition of tricalcium phosphate to dehydrate the CNFs did not improve their FS or FM. Conversely, sub-stitution with methanol effectively improved the dehydration process and significantly affected the mechanical properties of the CNFs. As the degree of CNF defibration increased, the physical properties of the specimens improved significantly. However, addition of CNFs to PMMA liquid to create CNF-reinforced PMMA did not improve the mechanical properties. Pure CNF specimens fabricated under particular conditions had higher FS and FM values than the control, suggesting that CNFs have potential as a “petroleum-free” alternative to acrylic resin denture base materials. Pure CNF would be potentially useful as a denture base material, and presum-ably applicable to computer-aided design/manufacture (CAD/CAM).