Recently, spark plasma sintering (SPS) systems have been used as high-temperature compressive creep testing devices. However, SPS systems can have complex temperature distributions within the experimental configuration that might lead to inaccuracies in the creep test results. For example, sample temperature profiles have been found to deviate from the initial temperature distribution as the sample is deformed during the creep test. Therefore, finite element analysis has been carried out on the SPS creep test mold configuration to evaluate the temperature distribution within an electrically conducing sample in three cases. Then, a multi-step thermal-electrical analysis was conducted to confirm the existence of and quantify a temperature deviation present during sample deformation. Thereafter, a systematic parametric investigation was performed to assess the effect of several geometrical parameters on the deviation in the sample temperature during deformation. Based on its results, recommendations for an optimal mold design that minimizes the sample temperature deviation during creep testing are provided. Finally, it is proposed that the thickness of the graphite felt used on the upper part of the die should be modified to further minimize the sample temperature deviation. The results of this study contribute to the overall understanding of the temperature distribution evolution and the effect of current during creep testing with an SPS apparatus and also provide practical geometrical recommendations for the use of SPS creep testing to achieve minimal sample temperature deviation.