Hospitals are among large-scale buildings with complicated energy system. Due to the significance of the hospital’s energy system in treating patients and general health, monitoring its resiliency is a crucial issue. Unfortunately, most of recent hospitals have been designed and developed, disregarding the importance of energy system’s resiliency. In this study, the resiliency of a hospital’s energy system has been investigated by quantifying the related criteria extracted from Hospitals’ Standard books and determining the system’s resiliency score. First, a hospital located in Tehran, Iran, has been selected as the case study, and its complicated energy system was modeled with Design-Builder software. Results of the simulation showed that the annual energy consumption of the current system was 3.08 GWh of electricity and 4.23 GWh of gas. Then, the energy system was separated into tiny wards, and the resiliency of each ward was measured using criteria linked to the resiliency of medical facilities by the scoring method. Calculating the weighted mean of the various wards yields the system’s overall resiliency. The mean resiliency score of the case study was calculated to be 4.13 (range from 1 to 5), which is considered a good value. However, the hospital’s power supply system which contributes the most to the total resiliency grade, owed the lowest score. Consequently, boosting the performance of this system may lead to a major influence on promoting the total energy system's resiliency.