The global waste crisis poses significant environmental challenges, with Southeast Asia being a major contributor to solid waste. Medan, Indonesia’s third largest city, is facing environmental challenges due to large amounts of plastic waste and was considered the dirtiest metropolitan city of Indonesia based on the assessment of the Ministry of Environment and Forestry and the Adipura 2020 program. This study proposes a sustainable approach by transforming plastic waste into fiberglass, a durable composite material, to produce fiberglass formwork, providing a sustainable alternative to traditional wooden formwork, since wooden formwork contributes to deforestation and environmental concerns. Building upon existing literature that separately reports the feasibility of producing fiberglass from plastic waste, and the utilization of fiberglass for formwork manufacturing, this study seeks to establish a direct link between plastic waste management and fiberglass formwork production. The objectives include evaluating its material potential, cost-effectiveness, productivity, and life cycle performance compared to wooden formwork. Results demonstrate that fiberglass formwork offers superior durability, dimensional stability, water resistance, 80% quicker installation, and extended lifespan up to 10 times longer than wooden formwork. This translates to cost-effectiveness by 54%, improved construction efficiency, and life cycle assessments show significant ecological cost and carbon footprint advantages, highlighting its environmental sustainability. This novel approach not only addresses plastic waste management but also reduces deforestation, aligning with global sustainability goals. Fiberglass formwork thus presents a compelling case for adoption in environmentally responsible construction practices.