The effective management of waste materials through innovative applications is essential for sustainable development. This study investigates the performance of sand and sand-tire mixtures as backfill materials behind retaining walls, focusing on their effectiveness in reducing lateral earth pressure and improving dynamic soil behavior. Tire-derived aggregates (STDAs), produced from recycled waste tires, were mixed with sand in varying proportions to evaluate their potential as a sustainable and efficient backfill material. A comparative analysis was conducted using a numerical retaining wall model developed in the RS2 finite element software. The performance of sand and sand-STDA mixtures was assessed under static loading conditions, with particular attention to lateral earth pressure reduction. Laboratory experiments were performed to validate the material properties and support the numerical findings. The results demonstrate that sand-STDA mixtures exhibit improved energy dissipation characteristics compared to sand alone, leading to a significant reduction in lateral earth pressure. These findings underscore the suitability of sand-STDA mixtures as a viable backfill material for retaining walls, offering a sustainable alternative that enhances geotechnical performance. This study provides valuable insights into the comparative behavior of sand and sand-tire mixtures, contributing to the development of sustainable and efficient construction practices in geotechnical engineering.