The goal of this study was to investigate the performance of mobile metallic temperature sensors in a packaged food processed in high power microwave assisted thermal sterilization (MATS) systems. A validated computer simulation model based on conformal finite difference time domain (FDTD) method was used to evaluate the influences of the microwave power intensity, probe tip geometry and diameter on the accuracy of the sensors. The simulation results revealed that a higher temperature zone was created near the probe tip. This temperature alteration was caused by the distortion of electric field at the probe tip area. Increasing the microwave power setting of MATS system amplified the temperature alteration. Proper sensor designs could help to reduce the temperature alterations. The flat probe tip was most sensitive to high power setting. Changing the probe tip to a spherical geometry and decreasing diameter of the probe significantly reduced the temperature alterations. (C) 2014 Elsevier Ltd. All rights reserved.