Slope instability caused by crest surcharge loading remains a critical geotechnical problem. While numerical methods are routinely used to assess such systems, their reliability depends on assumptions about soil–structure interaction and failure mechanisms. This study presents a combined numerical and experimental modelling investigation into the deformation and failure behaviour of pile-reinforced sand slopes subjected to applied loading. Small-scale physical model tests were conducted on uniform sand slopes constructed at a fixed inclination within a rigid tank. A loading plate was applied at the slope crest under quasi-static displacement control, supported by a group of piles embedded within the slope. The experimental approach follows established 1g physical slope modelling practice reported in the literature with emphasis placed on deformation observation and failure mechanism identification rather than rainfall-induced effects. To complement the physical tests, two-dimensional numerical analyses were conducted. The models were used to examine the influence of surcharge magnitude and pile representation on predicted stability and failure surfaces, enabling direct comparison with observed physical behaviour. The results indicate that pile reinforcement beneath the crest surcharge significantly affects the failure mechanism, slip surfaces, and the onset of global instability. Numerical analyses reproduced overall trends in stability improvement whilst exposing limitations in capturing localised deformation observed in the physical models. Merits and advantages of the proposed approach will be further explored in this contribution.