Infrared thermography has been increasingly used as an NDE tool for detection of defects in different types of components. At GE Global Research, the flash IR system is routinely used for inspecting for delaminations, porosity, and coating thickness and integrity. For defects such as delaminations and other larger defects, single-sided imaging, where the heat buildup due to the presence of defects can be visualized is used. However, in some cases, measurement of thermal diffusivity can also be used as an indicator of presence of damage. In this study, we report our findings on the accuracy of the diffusivity measurements using our flash IR system. The measurements were taken on a certified glass ceramic reference material and the experimental diffusivity values were compared with the certified values as measured by laser flash method. The diffusivity was calculated in both single-sided and thru-transmission modes and in both cases, the uncertainty in diffusivity was comparable to that of certified values.