Irreversible electroporation (IRE) is generally considered to be a non-thermal ablation modality. This study was designed to examine the relative effect of temperature on IRE ablation sizes for equivalent dose treatments with constitutive pulses between 1 and 100 µs. 3D in-vitro brain tumor models maintained at 10°C, 20°C, 30°C, or 37°C were exposed to 500V treatments using a temperature control algorithm to limit temperature increases to 5°C. Treatments consisted of integrated energized times (doses) of 0.01 or 0.1s. Pulse width, electrical dose, and initial temperature were all found to significantly affect the size of ablations and the resulting lethal electric field strength. The smallest ablations were created at 10°C and ELethal were calculated to be 1729, 1359, 929, 777, 483V/cm for 0.01s treatments with 1, 2, 4, 8, and 100µs pulses, respectively. At 37°C these values decreased to 773, 614, 507, 462, and 394V/cm, respectively. Increasing the dose from 0.01 to 0.1s at 37°C, resulted in statistically significant decreases (p<0.001) in ELethal for all treatments except for the 100µs group. This study found that IRE is a thermally mediated dose dependent ablation modality for pulses on the order of one microsecond. Tissue temperatures are not accounted for when determining ablative boundaries in treatment planning algorithms. This work demonstrates that data generated at room temperature may not be predictive of ablation volumes in-vivo and local temperatures should be accounted for in treatment planning.