Significant research has focused on the reliability of through-silicon-vias (TSVs) under conventional uniform thermal loading conditions such as accelerated thermal cycling (0–100 °C) or deep thermal cycling (−40–125 °C). This study analyzes the thermomechanical behavior of TSVs in 3D packages undergoing rapid local temperature fluctuations, as would be experienced in actual operation. A global/local finite element model is used to analyze the TSV behavior at various distances from the thermal fluctuation site. Transient thermal measurements, warpage and in-plane deformation measurements, as well as micro-Raman spectroscopy measurements are used to validate the model. The results reveal that the short term local temperature transients have minimal impact on the TSV stress state regardless of TSV location, implying that global package- induced stresses dominate.