Incorporation of betel leaf extract (BE) into chitosan and chitosan/vanillin (CH/Vn) blend films was carried out in order to improve the mechanical, thermal and antimicrobial properties of chitosan films. The influence of morphology, crystallinity and glass transition temperature (T g) on the mechanical properties of chitosan/betel leaf extract (CH/BE) and chitosan/vanillin/betel leaf extract (CH/Vn/BE) films was analyzed. The smooth homogeneous morphology, decreased crystallinity and shift of T g to a higher value resulted in improved mechanical properties. Scanning electron microscopy, atomic force microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and Fourier transform infrared studies indicated that inclusion of BE into CH/Vn led to enhanced physicochemical properties. The results of antimicrobial activity, oxygen gas permeability and contact angle measurements confirmed the significantly improved activity and hydrophilic nature of the blend films compared with those of pure chitosan. The authors confirmed that the plant-extract-doped polymer material can be a novel antimicrobial agent for food-packaging application. Addition of BE at a higher weight percentage is a major limitation that has a major influence on the properties of the blend films.