<p>Resistance spot welding (RSW) effectively joined Inconel 625 (IN 625) samples. This study examined how annealing heat treatment of cold-rolled sheets affects the microstructure and mechanical properties of resistance spot welded IN 625 joints. The microstructure and mechanical properties of the heat-affected zones (HAZ) of annealed sheets differed markedly from those of as-rolled sheets: fine recrystallized grains were absent in the HAZ of annealed sheets but present in the HAZ of as-rolled sheets. Furthermore, carbide accumulations were located closer to the weld button in annealed sheets than in as-rolled sheets. Microhardness measurements for annealed-sheet joints showed increased hardness in the fusion zone (FZ) and HAZ compared to the base metal (BM), while the HAZ hardness in as-rolled sheets was lower than in other joint regions. Pull-out fracture (PF) occurred in annealed sheets at low and moderate welding currents and in as-rolled sheets at high welding currents, whereas tearing failure (TF) occurred in annealed sheets under high welding currents. As the fracture mode shifted to TF in annealed sheets, as-rolled IN 625 exhibited a higher fracture load, while annealed IN 625 showed greater fracture energy under the same welding conditions.</p>