Thermographic imaging technique provides a practical tool for the detection of subsurface delaminations in concrete from a distance without direct access to the surface. In the previous study, a numerical model to predict the thermal contrasts resulting from subsurface voids (i.e., delaminations) in concrete under a given set of environmental conditions was developed using the finite element method. The model was verified using the experimental test data, and the results indicated that the model could be an effective tool to support the thermography inspection of the concrete. In this present study, the use of the verified model to evaluate the effects of other key parameters expected to influence the detectability of the subsurface voids, such as the depth and thickness of a subsurface delamination. The effect of these parameters on the thermal contrast developed on the surface above a subsurface delamination was assessed under a specific set of environmental conditions. The results shown that the maximum thermal contrast decreased exponential by a constant multiple of 0.98 as the void depth increased and the maximum thermal contrast increased nonlinearly with increasing thickness of the void.