The effect on mechanical properties and microstructure of SAC 387 lead free solder alloys by addition of 1 wt% Au nanoparticles was studied. Also the effect on tensile properties at different temperatures and strain rates was investigated. The powder metallurgy process followed to make the SAC 387 + 1 wt% Au alloy was found to result in mechanical alloying and complete dissolution of Au in the β-Sn matrix resulting in the formation of fine AuSn4 intermetallics. The addition of 1 wt% Au to the base alloy SAC 387 resulted in an increase in yield (YS) and ultimate tensile strengths (UTS) at all temperatures and strain rates without any decrease in the total elongation (TE). Both YS and UTS were found to decrease with increase in temperature at any given strain rate for the base alloy SAC 387 as well as SAC 387 + 1 wt% Au alloy. On the other hand, for both alloys, YS and UTS were found to increase with increase in strain rate at any given test temperature. Although the trends in change of uniform elongation (UE) and TE with temperature and strain rate were not as monotonic as in the case of YS and UTS, in general, the UE and TE increased with increasing temperature and decreased with increasing strain rate. The results were explained based on the likely deformation mechanisms operative in these alloys at different strain rates and temperatures. © 2018, The Indian Institute of Metals - IIM.