Microwave sensing represents a promising approach for non-invasive tissue temperature monitoring during hyperthermia treatment. Tissue mimicking phantom materials with corresponding dielectric properties and suitable for heating experiments are essential for preliminary methodical investigations as well as for the development of the measurement hardware. In the present paper, a fat tissue mimicking phantom material is investigated depending on the temperature in the range between 30 °C and 50 °C and the frequency range between 0.5 GHz and 7 GHz. The measured data are modeled by means of a two-pole Cole-Cole model and the temperature dependence of the Cole-Cole parameters is fitted by means of a second-order polynomial. The results show that this material imitate the dielectric properties of real fat tissue as well as its very low temperature dependence appropriately and can be used for practical experiments.