In this work, we present a simple analytical model for electrothermal heating in multifinger bipolar transistors under realistic operating condition where all fingers are heating simultaneously. The proposed model intuitively incorporates the effect of thermal coupling among the neighboring fingers in the framework of self-heating bringing down the overall model complexity. Compared to the traditional thermal modeling approach for an n-finger transistor where the number of circuit nodes increases as n2, our model requires only n-number of nodes. The proposed model is scalable for any number of fingers and with different emitter geometries. The model is validated with 3-D thermal simulations and measured data from STMicroelectronics B4T technology. The Verilog-A implemented model simulates 40% faster than the conventional model in a transient simulation of a five-finger transistor. © 1963-2012 IEEE.