This study reports ascorbic acid adsorption/release performance and antibacterial activity of chitosan composite microcapsules containing terpolymer of glycidyl methacrylate (GMA), maleic anhydride (MA) and N-tert-butylacrylamide (NTBA). The effects of amount of chitosan composite microcapsules, solution pH, ascorbic acid concentration and contact time on the adsorption of ascorbic acid by chitosan-ter (GMA-MA-NTBA) polymer microcapsules were studied. The maximum ascorbic acid adsorption was observed for 0.075 g of microcapsules under following conditions; ascorbic acid concentration: 10 mg L−1, pH 7.35, temperature: 35 °C and contact time: 1 h. Antibacterial activity of chitosan-ter (GMA-MA-NTBA) polymer microcapsules was tested against Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25113, Klebsiella pneumoniae ATCC 700603, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212 and Salmonella enteritidis ATCC 13076 bacterial strains. In vitro antibacterial studies demonstrated that chitosan microcapsules with 0.25% ter (GMA-MA-NTBA) polymer (by mass) were more effective on inhibiting of bacterial growth. Plain glutaraldehyde-chitosan beads showed no antibacterial activity, indicating that ter(GMA-MA-NTBA) polymer content was responsible for the antibacterial activity of the chitosan-ter(GMA-MA-NTBA) polymer microcapsules. Graphic Abstract: [Figure not available: see fulltext.]