The development of lead-free solder alloys suitable for applications that require high- temperatures is essential to fulfilling the growing demand for dependable alternatives to conventional lead-solder alloys. The studies were focused on the effect of indium addition on the morphology alteration and the wettability of commercial Sn10Cu-based solder alloys. The Sn10Cu was added with 0.5, 1, 3, and 5 wt.% of indium and prepared by using the casting method. The microstructure of bulk solder was observed using SEM with EDX, while the wetting angle was measured to evaluate the wettability of solder alloys. Adding indium significantly changes the phase formation of Sn10Cu solder alloys. The Cu3Sn phase boundary is shifted with indium content up to 5.75 wt.%. The Cu6Sn5 IMC was greatly refined and evenly distributed following the addition of 3 wt.% and 5 wt.% indium. The wetting angle of Sn10Cu decreases when indium is added. In comparison to Sn10Cu, the wetting angle of Sn10Cu-5In solder alloy decreased by 30.8%. The lowered melting temperature of indium suggests that it can effectively improve the wettability of Sn10Cu solder. The lowered melting temperature will allow for better fluidity during soldering.