The development of sustainable polymer films with enhanced mechanical integrity is crucial for emerging applications in packaging, biomedical devices and flexible materials. In the present study, pure chitosan, cross-linked chitosan and grafted chitosan biopolymer composites were synthesized and systematically investigated with respect to their film-forming behavior, mechanical properties and structure–mechanical relationships. Structural modifications were confirmed using FTIR and X-ray diffraction analyses, while surface morphology was examined by SEM. Mechanical properties including tensile strength, elongation at break and Young’s modulus were evaluated using standardized tensile testing. Cross-linking and grafting significantly improved tensile strength and dimensional stability while reducing brittleness associated with pure chitosan films. The observed enhancement in mechanical performance is attributed to reduced crystallinity, improved stress transfer and restricted polymer chain mobility induced by chemical modification. The results demonstrate that modified chitosan composites are promising candidates for eco-friendly structural and functional film applications.