<p>The development of green structural retrofit materials that are heat resistant is a crucial step towards enhancing the sustainability and safety of modern construction practices. Development and testing of natural fiber-based composite materials not only cater to sustainable development goals but also render better results comparatively. Current work focusses on natural fibers such as bamboo and banana which were chemically treated with flame retardant additives (boron compounds) to enhance their heat resistance and reduce flammability. The surface modified fibers were then incorporated into a polymer matrix (epoxy resin) to create composite materials. Flame-retardant versions of bamboo and banana fiber reinforced with epoxy resin composites were individually developed. After being heated, the fibers were immersed in a sodium hydroxide solution, which allowed the solution to seep into the fibers’ capillaries. Incorporating boron into the reinforcing fibers altered the flammability of banana and bamboo fibers with epoxy composites. When the boric acid was used with the treated fibers, a V-1 UL-94 rating with after flame burning rate of 51&#xa0;s and 13&#xa0;s for bamboo and banana fibers respectively was attained. Results showcased that the surface modified bamboo fiber composites exhibited better flame-retardant characteristics while the banana fiber composites exhibited 21% better flexural characteristics. The developed natural fiber composites are the viable candidates for structural retrofitting applications to create high-performance, sustainable building materials contributing to safer and more resilient infrastructure.</p>