Today, waste management and recycling have critical importance given the dwindling natural resources and to create powerful technologies for a green future. One of these strontium hexaferrite powders were produced by mechanochemical process using mill-scale and strontium carbonate from obtained celestite ore. The strontium carbonate and the mill scale were prepared in stoichiometric ratio, and mechanochemical process was applied for 16 h to produce hard-ferrite powders. Following the mechanochemical synthesis process, powder mixture was annealed at 850–1000 °C temperatures. The morphology, crystal structure and phase composition of strontium hexaferrite powders caused the magnetic properties to change according to the annealing temperature. As a result of the studies, the most suitable annealing temperature was determined as 975 °C. The Hc, Br and (BH)max of produced powders correspond to 5505Oe, 347 mT and 5.77MGOe at 975 °C, respectively. The Curie temperature of the annealed powders was determined as 474 °C. Display omitted •Strontium hexaferrite powders are successfully produced using a mill scale wastes.•The phase ratios and types in the strontium hexaferrite structure changed with the annealing temperature.•The powder shape of the strontium hexaferrite turned into a hexagonal structure with the increase in annealing temperature.•The best magnetic performance of strontium hexaferrite powders was obtained in annealed at 975 °C.•(BH)max. of annealed strontium hexaferrite powders was increased up to 5.77 MGO.