A new method for the measurement of the thermal diffusivity in metals, using transient conditions, is demonstrated. This method is using the principle of superposition of thermal loads. Only time measurements are required, and no accurate temperature and heat flow rate measurements are needed. The method utilizes the Seebeck effect for the measurement of the time dependence of the temperature. A solution of the heat transfer equation for the model pertinent to the described method is derived, and results obtained for several materials are presented.