In mineral processing operations of sulfide ores, the valuable nickel and copper-bearing minerals are concentrated, while the lower-value minerals such as pyrrhotite are rejected to the tailings. In recent years, nickeliferous tailings reprocessing has attracted significant attention due to the declining ore grades and an increased focus on the environmental threats posed by large tailings storage facilities. Thermo-concentration is a potential process for tailings treatment. Investigations since the 1970s have shown that thermo-concentration can recover nickel from the tailings while avoiding SO2 emissions. However, it is a highly endothermic process. Iron is added to the pyrrhotite tailings, and the mixture is thermally processed to produce an alloy phase assaying 10–20% nickel. In the present research, microwave radiation (2450 MHz) was utilized to thermo-concentrate nickel from the mixtures of nickeliferous pyrrhotite, iron oxides, and metallurgical coke. Microwaving of the reaction mixtures at 800 W was found to be sufficient to initiate the thermo-concentration process and form an alloy containing greater than 10% nickel.