IC designers require fast and accurate methods of simulating immunity of ICs to ESD events to adequately predict and analyze ESD issues. The common method of predicting electromagnetic field coupling from an ESD gun to an IC, however, requires substantial simulation time and does not typically account for the full IC layout. Here we propose an efficient methodology for calculating the electromagnetic field coupling from an ESD gun to an IC while fully considering the non-linear circuit elements in the IC core. Voltages and currents within the IC are found by merging full-wave simulations of an ESD gun with a SPICE model of the IC and the coupled electromagnetic energy. The capability of the proposed method was verified through experiments on a pseudo-integrated circuit structure. Results show the promise of the method. This hybrid modelling method can significantly accelerate simulation time compared with traditional full-wave modelling techniques and can allow the designer to better explore the variation in coupling that occurs with small changes in the test setup, such as the position and orientation of the gun and IC.