An automobile seat’s thermal performance can be challenging to quantify since it requires comprehensive human subject testing. Seat manufacturers must rely on subjective ratings to understand how the construction of a seat and its underlying heating and cooling technology may compare to other seats. Other factors may influence seat ratings published by global marketing information services companies (e.g., JD Power and Associates). In particular, occupants may be biased by the vehicle class in which a seat is installed and by how much the contribution of a specific vehicle’s HVAC system performance affects the perception of seat thermal comfort. Therefore, there is a need for an objective testing methodology that does not rely on human participants but is still capable of producing a thermal performance rating in terms of established thermal comfort scales.This paper describes a methodology that uses in situ seat testing in a fixed temperature environment to derive the seat’s thermal characteristics. This characterization can subsequently be input to a human thermal physiology model to simulate thermal perception for a scenario of interest (e.g., a transient heat-up or cool-down), which may differ considerably from the original test environment. The test procedure involves placing a heated test device onto a seat and measuring the heat flux and temperature response at its surface. The test conditions are subsequently reproduced within a thermal model. The effective seat properties and heating characteristics are derived by matching the simulated thermal response with the measured response captured in the test data through a numerical optimizer. The study described in this paper includes a detailed description of the test protocol, the thermal model of the seat, the numerical optimization procedure used to derive its effective thermal properties, and a quantitative comparison of the simulated seat characterization results with measurements. Note that human thermal perception predictions are outside the scope of this paper but may be reported in future work.