This research focuses on the development of a sustainable approach for the generation of free-standing, highly transparent and flexible films of chitin nanocrystals (ChNCs) from shrimp shells. ChNCs were extracted by acid hydrolysis and subsequently treated in an alkaline environment to produce surface-deacetylated chitin nanocrystals (CsNCs). The effects of deacetylation on the size, morphology and colloidal stability of the nanocrystals were systematically investigated using scanning electron microscopy (SEM), dynamic light scattering (DLS) and zeta potential analysis. The reaction time was optimized to improve the degree of deacetylation and thus particle interactions, which in turn had a direct impact on the structural and mechanical properties of the films. To further enhance the functional properties of the films, natural polyphenols (epigallocatechin gallate, tannic acid and the methanol-insoluble fraction of hardwood lignosulfonate) of different chain length and content of hydroxyl groups were incorporated as crosslinkers, strengthening the hydrogen bonding network and significantly improving mechanical strength, water resistance, and bioactivity.[1] The resulting films exhibited no dissolution observed up to 7 days of soaking in water, strong antioxidant and antimicrobial properties, including bactericidal activity against both Gram-negative (E. coli) and Gram-positive (S. aureus) bacterial strains as high as 99.99%. Additionally, glycerol was explored as a plasticizer to optimize flexibility and mechanical performance while maintaining the films’ hierarchically ordered structures. This work provides critical insights into the self-assembly of chitin-based films and demonstrates the potential of utilizing seafood byproducts for the development of high-performance, biobased materials with high applicability potential.