Renewable and biodegradable packaging sourced from plant biomass holds promise as a substitute for non-biodegradable petrochemical-based plastics. However, the thermo-processability of bio-based packaging often fall short for practical use, specifically in multi-layer and flexible food packaging. To address this challenge, a novel approach is proposed to synthesize flexible cellulosic packaging from wastepaper that leverages microwave irradiation and ionic liquids-based wet film casting technology. This method involves transforming wastepaper into a homogeneous ionic liquid-cellulose solution, which is then cast into flat membranes and regenerated using antisolvents to produce a thermoplastic cellulosic film. The resulting films exhibit tunable tensile strength and thermoplastic behavior by virtue of differences in ionic liquid content. Additionally, it boasts a reduced environmental footprint throughout the manufacturing and end-of-life stages. By exclusively utilizing renewable feedstocks and green manufacturing technology, this strategy produces a thermoplastic cellulosic film which could be a promising solution to bio-based flexible packaging.