Thermal fatigue performance and creep resistance of soldered connections are crucial to the integrity and reliability of microelectronics, optoelectronics and photonics packaging systems. In this work, creep and thermal fatigue behaviours of lap shear joints soldered by a tin-based nanocomposite solder were characterized at different temperatures, with a comparison to a traditional Sn60Pb40 solder. The results show that the nano-composite solder has much better creep resistance and thermal creep fatigue property than the Sn60Pb40 solder. This is mainly due to the uniformly dispersed nano-sized Ag particles that have provided effective impediment to dislocation movement and grain boundary sliding, in addition to the alloying effect. The creep fractography analysis by SEM shows that a progressive shear deformation occurred as the main creep fracture mechanism. Sn60Pb solder joints deform dominantly by transgranular sliding, while the nano-composite solder joints creep by intergranular mechanism through grain boundary sliding and voids growth.