Raw chitin nanofibers (CNF) through an 8-min high-power sonication process were successfully prepared. Well-preserved nanofibers with diameters of 50–100 nm and lengths of 3–10 μm were observed by atomic force microscopy. The high aspect ratio induced strong entanglement under high shear rates, leading to a typical nanofiber four-region shear-thinning behavior. These native chitin nanofibers were incorporated into chitosan film-forming solutions at different concentrations. FTIR results indicated intermolecular hydrogen bonds between CS and CNF. Tensile strength was significantly enhanced with the inclusion of CNF, with the highest stress at 30% CNF incorporation. Elongation at break increased up to 35% with 10% CNF concentration, gradually decreasing with higher CNF content. CS with 20% addition of CNF content was chosen for curcumin addition considering the high mechanical performance and low grammage value. Oxygen transmission rate reduced slowly with increasing CNF concentration, and a significant drop by about 90% was observed upon curcumin inclusion. UV blocking performance and antioxidant ability were drastically improved after curcumin inclusion. The utilization of raw CNF as a film reinforcement nanofiller offers several advantages, including ease of preparation, higher aspect ratio, longer length, and superior mechanical performance. CNF-reinforced chitosan films emerge as potent candidates for functional food packaging materials. Display omitted •Raw chitin nanofiber with a high aspect ratio was prepared by ultrasonication.•A typical nanofiber four-region shear thinning behavior was observed on raw chitin nanofiber suspension.•Raw chitin nanofiber significantly improved the elongation at break and tensile strength for chitosan films.•The incorporation of curcumin enhanced the chitosan/chitin nanofiber film antioxidant and oxygen barrier ability.