Due to the complexity in the development of highly nonlinear models for seismic isolators, engineers tend to use more practical ones such as smoothed or sharp bilinear models. It has been shown that differences in hysteresis characteristics may lead to variance in performance parameters, resulting in possible overdesign or underdesign. In this study, to assess the effect of the modelling approach on seismic performance, high damping rubber bearing system was designed and evaluated in terms of structural performance for a selected hospital building. Commonly used bilinear and highly nonlinear isolator hysteresis models from the literature were adopted, and structural models were created for 2475 years return period earthquake level. Three-dimensional nonlinear time history analyses were conducted on the 10-story building model under a set of 11 ground motions. Structural performance is evaluated and compared in terms of maximum isolator displacements, base shear reactions, story accelerations, inter-story drifts. Significant variation in the superstructural response is observed for the hospital building when bilinear models were used instead of more accurate nonlinear models.