The mining industry plays a crucial role in the economic development of many nations, but it also generates substantial waste, mainly in the form of mine tailings, which are commonly stored in dams, causing often environmental concerns. To address this issue, innovative methods are being explored for reprocessing and reutilizing these side streams. This study focuses on applying mechanochemical activation (MCA) to treat iron ore mine tailings from Kiruna, Sweden, transforming them into supplementary cementitious materials (SCMs). The MCA process resulted in extensive amorphization of the main crystalline mineral phases such as phlogopite, feldspars, apatite, and hematite. The enhanced pozzolanic activity after MCA treatment was confirmed through the strength activity index (SAI), Frattini test and R3 method. This case study highlights the significant potential of mechanochemical treatment in revalorizing iron ore mine tailings, contributing to their sustainable utilization and mitigating the negative environmental impact associated with these waste materials.