World resources of iron ore amount to 190 billion tons, generating circa 5–7 billion tons of tailings yearly. Iron ore tailings have been deposited in tailing dams or, more recently, stocked in large thickened-tailings piles, both high-risk facilities. An interesting alternative destination is the reuse of these materials in geotechnical earthworks, introducing them in the circular economy, while lessening the exploitation of natural materials. This paper shows the geotechnical characterization of iron ore tailings generated in a Brazilian mining plant, comprising geotechnical classification, determination of compaction optimum parameters at Proctor standard energy, and assessment of shear strength and hydraulic conductivity at optimum water content and maximum dry unit weight. The material is classified as a silty sand (SM), with no cohesion, optimum water content of 6%, maximum dry unit weight of 16.6 kN/m3, friction angle of 35.6° and permeability coefficient of (1.1 ± 0.1) × 10–5 m/s. Despite being a synthetic material, these filtered iron tailings behave as fine silty sand and could be used in several geotechnical applications. As a next step to assess suitability for earthworks, environmental tests under service conditions should be carried out.