A novel eco-friendly method was established to synthesize ultra-small silver nanoparticles (AgNPs)-decorated chitosan films with strong antibacterial activity. The AgNPs were produced by reducing AgNO3 with glucose derived from sucrose hydrolysis under alkaline conditions (pH ∼12.06) in a chitosan matrix, yielding spherical particles (∼8.6 nm) at an optimal 1:4 Ag+ to sucrose molar ratio. Mixing the resulting Chit-AgNPs colloid with glycerol in equal volumes produced a biodegradable Chit-AgNPs/G1 film with mechanical properties that meet biodegradable plastic standards. Antibacterial tests against B. subtilis and E. coli revealed that the film exhibited markedly higher efficacy than its precursors and was comparable or even superior to standard controls (amoxicillin and betadine). Overall, the Chit-AgNPs/G1 film demonstrates exceptional antibacterial performance, positioning it as one of the most effective chitosan–AgNP composites reported to date. © 2025 The Authors