The effects of minor alloying additions of Ni and Bi on the electromigration (EM) reliability and nanomechanical properties of Sn-Ag-Cu (SAC405 and SAC1205, noted as SAC) solder joints were investigated. The nanomechanical properties of the solders were measured by nanoindentation with the continuous contact stiffness (CSM) mode. The EM results indicated that the SAC-Ni solders exhibit better lifetime than others. The EM fracture behaviors of the solder joints were governed by the intermetallic compounds formed in the solder joints. The fracture occurred at the redistribution layer and under bump metallization/solder ball interface for SAC-Bi and SAC-Ni, respectively. Both the nanohardness and the elastic modulus of SAC solders are clearly enhanced by the minor alloying additions of Ni and Bi.