This study investigates the performance of two waste materials, steel slag and construction and demolition waste (CDW), as potential backfill materials for reinforced earth (RE) applications under cyclic loading conditions. Consolidated-undrained cyclic triaxial tests were conducted on the materials to investigate the material behavior. The study also assessed the influence of incorporating geogrids on the cyclic performance of the materials. Both the waste materials exhibited cyclic behavior similar to that of conventional sand, with maximum deviator stress observed in slag, followed by CDW. The presence of slightly higher fines content in slag and CDW resulted in increased excess pore pressure compared to sand. The incorporation of geogrid enhanced the cyclic strength of both slag and CDW. In the first cycle, an improvement of 26% and 20% was observed with the inclusion of geogrid in slag and CDW, respectively, at a frequency of 1 Hz. In addition, the use of geogrid resulted in a reduction in excess pore water pressure generation. At a given frequency, the shear modulus of slag and CDW was found to be higher than that of sand. In the initial loading cycle, the shear modulus of slag was 54% higher, and CDW was 26% higher compared to sand. With the inclusion of geogrid, the dynamic shear modulus of sand, slag and CDW in the first cycle improved by 18%, 28%, and 25%, respectively. Sand exhibited a higher damping ratio compared to slag and CDW. However, the influence of geogrid on the damping ratio was found to be negligible. Furthermore, a 2D numerical investigation was conducted to explore the potential implementation of slag and CDW in practical applications, specifically in RE walls under railway loading. Numerical simulations revealed a significant reduction in wall deflection when slag or CDW was used as backfill compared to conventional material. The peak horizontal facing displacement values were found to reduce by 48% and 32% for slag and CDW, respectively, when compared to the use of sand.