This paper presents an electrothermal model of ferromagnetic cores dedicated for SPICE software. The form of this model, dedicated to be used in power electronics applications, is presented and the procedure of estimating magnetic, geometric and thermal parameters of the presented model is proposed. The correctness of the proposed model is verified by comparing the calculated and measured characteristics of the selected ferromagnetic cores operating at different values of flux density, frequency, ambient temperature and cooling conditions. The satisfied agreement between the results of calculations and measurements is obtained.