The study examines the impact of backfill parameters on the static and seismic response of Cantilever retaining walls (CRWs) using Plaxis 2D FEM software. Key parameters include backfill density (1 to 2 g/cc) and internal friction angle (20° to 28°), with CRW heights from 4 to 10 m. For 4-m and 6-m walls, stability was maintained in both static and seismic analyses across all parameters. Lighter backfill materials reduced vertical deformations, with seismic deformations lower than static ones, while lateral deformations at the stem were consistently higher in seismic analysis. For 8-m and 10-m walls, stability was achieved with backfill densities up to 1.6 g/cc in static analysis and 1.4 g/cc in seismic analysis. Higher internal friction angles reduced deformations and earth pressure. Lighter backfills showed improved flexibility, reduced earth pressure, and enhanced stability. The study underscores the importance of backfill parameters, suggesting CRWs up to 10 m can use lightweight fill materials without compromising structural integrity, provided backfill density and friction angles are carefully considered.