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The main aim of current study is to explore the potential of deep eutectic solvent (DES) as plasticizer. The influence of different choline chloride–citric acid monohydrate (ChCl–CAM) molar ratios was investigated based on the properties of the selected biopolymer film (BF). It should be highlighted that using DES as a plasticizer had improved the properties of BF and the DES at its eutectic point (ratio 1:1) exhibited minimal plasticizing effect because of the self-interaction between ChCl and CAM. The melting temperature, tensile stress, tensile strain, modulus, moisture absorption and water vapor transmission rate are within the range of 124.63–180.77 °C, 3.71–9.26 MPa, 9.69–32.53%, 22.80-122.08 MPa, 1.39–42.10% and 1.05–5.44 mg/m2s, respectively. It was also observed that the plasticizing effect decreased when the ChCl molar ratio was higher, whereas the effect was induced with increased CAM molar ratio. The BFs also exhibited antioxidant activities, such as free radical activity (32.80–38.25%) and ferric reducing antioxidant power (FRAP, 0.76 to 1.45 mM FeSO4). These results showed that the availability of choline cation (C5H14ON+) of choline chloride and functional group (–COOH) of CAM in DES are the key factors for its plasticizing property.