The eutectic Sn3.8Ag0.7Cu alloy is widely considered a leading Pb-free replacement for the eutectic Pb-Sn solder alloy in electronic packaging where creep deformation and rupture is a major concern. In this study, creep rupture behavior of Sn-Ag-Cu solder alloy was investigated under the isothermal condition. Creep tests were conducted under a range of stresses and temperatures. Creep lifetime data were analyzed by the combined time-temperature equations following the Sherby, Larsen-Miller, and Manson-Haferd approaches. From these analyses, a series of material parameters were obtained from the experimental data. The results showed that the Manson-Hanferd method provided a better correlation with the creep rupture data. The mechanisms of creep deformation and rupture at different time-temperature combinations are discussed.