To determine the maximum allowed power dissipation in a power transistor, it is important to determine the relationship between junction temperature and power dissipation. This work presents a new method for measuring the junction temperature in a SiC bipolar junction transistor (BJT) that is self-heated during DC forward conduction. The method also enables extraction of the thermal resistance between junction and ambient by measurements of the junction temperature as function of DC power dissipation. The basic principle of the method is to determine the temperature dependent I-V characteristics of the transistor under pulsed conditions with negligible self-heating, and compare these results with DC measurements with self-heating. Consistent results were obtained from two independent temperature measurements using the temperature dependence of the current gain, and the temperature dependence of the base-emitter I-V characteristics, respectively.