This research aimed to study the effect of pre-deformation by torsion and the addition of ZnO nanoparticles on the microstructure and tensile behavior of Sn-based soft solder alloys. The used alloys are Sn-3Ag-0.7Cu (SAC307) and Sn-3Ag-0.7Cu doped with 0.3wt%ZnO nanoparticles SACZ3(307). Pre-deformation increases the dislocation density consequently the lattice strain is increased. Applying pre-torsional deformation before the tensile test resulted in the enhancement of the mechanical properties σy0.2 , σf and Χp for both SAC (307) and composite solders at different working temperatures. These changes in mechanical properties depend on the internal structure of both solders since deformation generates an excess of mixed defects. Also, the dispersed intermetallic compounds (IMCs) particles hinder the motion of dislocations. This study includes new and novel results about the behavior of fracture strain εf with deformation at the different working temperatures. According to the obtained activation energy Q values, the dislocation-IMCs interaction is the deformation mechanism taking place in both alloys.