Circular economy envisages resource efficiency and minimization of the negative impacts of waste on the environment and human health. This work considers municipal solid waste incineration bottom ash (IBA) for safe use in geotechnical works, through physical, chemical, ecotoxicological, and geotechnical analysis of samples with different weathering periods. Low leaching potential and no relevant ecotoxic effects were found for IBA. Better compaction was obtained for IBA mixtures with sand. All materials showed reasonable permeability after compaction. IBA stiffness and shear strength values, consistently assessed through different tests, were within dense granular soils range. Weathering seems to positively influence IBA geotechnical properties, which in any case seem compatible with environmentally safe and sustainable geotechnical applications.