Compared with single-module applications, unbalanced stray parameters come about frequently in the process of installing paralleled IGBT modules, which could result in some distinctions of current sharing and temperature distributions. To focusing on depicting this practical issue, a novel dynamic electrothermal model extended to paralleled systems is proposed in this paper to establish a comprehensive transient model to characterize the relations of power losses, junction temperature, and unbalanced parasitic elements. The model can describe the interactions of current distributions and thermal dissipations between paralleled modules. In addition, the variation of unbalanced temperature during transient process can be obtained with the proposed electrothermal model. First, the stray inductance parameters in the paralleled branches are analyzed in detail by finite-element-method simulation tool. And based on impedance analysis, an improved power loss model is built up, considering the interaction of paralleled devices. Moreover, by the method of resistor-capacitor networks extracted from numerical simulations of 3-D structural model, the transient thermal impedance of devices and cooling system is obtained for fast and accurate electrothermal cosimulation of the paralleled system. Experimental results are carried out to verify the proposed model and coincide with the theoretical analysis.