In recent years, sustainable alternatives to synthetic, nonbiodegradable polymers have become crucial for advancing eco-friendly solutions in soft electronics and packaging. This work explores two biopolymer film modification strategies—plasticization and layered film assembly—for potential applications in these fields. In the plasticization approach, natural polymers such as chitosan and agarose were plasticized using glycerol to reduce the number of hydrogen bonds among the chains, which enhanced chain mobility. This results in improved flexibility and stretchability of the polymer films. Plasticized chitosan films demonstrated remarkable elongation at break (~110%) with a Young’s modulus on the same order of magnitude as human skin. The films also exhibited high optical transparency and high water vapor transmission rates, allowing sweat vapor to pass through the biopolymer-based devices, which is key for comfort in wearable applications. The swelling and weight loss behavior of the films, driven by water uptake and glycerol leaching, were studied to assess their properties in different conditions. Silver nanowires (AgNWs) were printed on the biopolymer films to form conductive pathways, enabling functional circuit patterns. Chitosan-based substrates were used to develop wearable electronic devices such as EMG and strain sensors, which underwent enzymatic degradation in lysozyme. Following degradation, AgNWs were recovered and reused in subsequent device fabrication, demonstrating material circularity. For packaging applications, sustainable biopolymer films, comprising agarose and shellac, were developed using the layered film assembly technique. Agarose offers mechanical strength but does not have good barrier properties. On the other hand, shellac offers high barrier properties and can be used as a coating on other materials or polymer layers. In this work, shellac coating on the agarose layer reduced the water vapor transmission and significantly improved its barrier properties. The layered films exhibited 35–42% stretchability with moderate strength and could be thermoformed above shellac’s glass transition temperature into various shapes such as boxes, pyramids, and cylinders. The layered films effectively preserved fruit by minimizing weight loss and maintaining taste, while their transparency allowed visual inspection of fruit quality without compromising the packaging. Together, these biopolymer film modification strategies demonstrate a path toward high-performance, biodegradable materials for soft electronics and packaging.