BACKGROUND The usage of natural polysaccharides is attractive to researchers around the world. At the same time, non‐/low‐toxic crosslinkers prepared by polysaccharides are expected to fabricate protein‐based films in many fields. Herein, different dialdehyde polysaccharides (DPs) were successfully synthesized and applied to prepare gliadin‐films under alkaline conditions. The functional properties and formation mechanisms of the films were fully investigated. RESULTS The results showed that the mechanical properties, water‐resistant properties, thermal stability, and antibacterial properties of the gliadin‐films were improved by DPs and alkali treatment. Particularly dialdehyde dextrin (DAD) crosslinked gliadin‐films showed the highest tensile strength, but no additional effect on their elongation, or advancement on the other functional properties. The film‐forming mechanisms indicated that Schiff base bonds, hydrophobic interactions, electrostatic interactions, and hydrogen bonds were the main forces in the films, supporting their improvement in functional properties. CONCLUSION DPs, especially DAD, can be a promising crosslinker in fabricating gliadin‐films. These findings have shown great promise to seek an effective crosslinker for fabricating gliadin/protein‐based packaging. © 2023 Society of Chemical Industry.