This experiment explores incorporation of hemp fiber and FlyAsh Geopolymer Sand (FGPS) as composite materials in reinforced concrete, aiming to enhance its mechanical properties and high-temperature resistance. The research focuses on the synergistic effects of these natural and mineral additives on the structural performance, sustainability, and thermal stability of concrete. Hemp fibers, recognized for their tensile strength and flexibility, are incorporated to enhance the ductility and fracture resistance of the concrete matrix. Simultaneously, FGPS is utilized to replace a portion of traditional Fine aggregates, capitalizing on its lightweight properties to improve the concrete’s resistance to high temperatures. The study provides insights into how these innovative materials can contribute to the development of more durable and sustainable concrete solutions. Comprehensive experimental analysis, including compressive strength, flexural strength, and high-temperature tests, was conducted to assess the performance of the modified concrete. The results demonstrate significant improvements in both mechanical properties and high-temperature performance in comparison to conventional concrete. The incorporation of hemp fiber and FGPS not only enhances the sustainability of the concrete but also provides a viable solution for construction applications requiring enhanced mechanical robustness and thermal resilience. This research contributes in development of greener and more resilient construction material, paving the way for innovations in sustainable infrastructure.