<p>Iron Ore Tailings (IOTs), a major fine-grained deposit obtained from the beneficiation of iron ores, represent one of the major productions among the mining waste all over the world. Their safe disposal and potential reuse in civil infrastructure are gaining research consideration among the scientists and researchers. This study investigates the use of IOTs as an alternative backfill material for retaining walls structures by integrating detailed experimental approach and numerical modelling techniques. Samples collected from two different operational tailings dams, which underwent physical, chemical, and geotechnical characterization. The results direct that IOTs possess favourable engineering properties suitable for use as backfill material, including high specific gravity (3.16–3.20), good compaction potential (MDD 2680–2710 kg/m³), adequate shear resistance (friction angles ‘ϕ’ = 49–51°, cohesion ‘C’ ≈ 10 kPa), and moderate permeability ‘k’ = (3.70–4.10) × 10⁻⁵ m/s. Environmental assessments, including leachate and physicochemical analysis, revealed that IOTs fall within safe limits for non-hazardous classification, ensuring their suitability from an environmental perspective. Numerical simulations using Limit Equilibrium and Finite Element methods displayed improved stability performance for retaining walls backfilled with IOTs compared to conventional sand; for example, under dry conditions, the best-performing IOTs sample yielded a Factor of Safety (FoS) of 3.603 and a Strength Reduction Factor (SRF) of 1.89, compared to 3.394 and 1.73 for sand, respectively. The integration of experimental and numerical results confirms that IOTs can serve as a sustainable, technically feasible, and environmentally safe replacement for natural aggregates in geotechnical applications. This study contributes to sustainable construction practices and promotes circular economy principles by valorising mining waste.</p>