In this paper, passive thermal management of an electric vehicle (EV) battery pack with phase change material (PCM) is studied numerically. When the temperature in the cells increases, and consequently in the submodule also, the heat is absorbed through melting of the cooling jacket which surrounds the cells. This, in turn, creates cooling effects in the cell and the battery pack. A finite volume based numerical model is used for the numerical simulations. The effects of different operating conditions are compared for the submodule with and without the PCM. The present results show that a more uniform temperature distribution is obtained when the PCM is employed which is in agreement with past literature and experimental data. The results also imply that the effect of PCM on cell temperature is more pronounced when the cooling system operates under transient conditions. The required time to reach the quasi-steady state temperature is less than 3 h, and it strongly depends on the heat generation rate in the cell. The maximum temperature of the system decreases from 310.9 K to 303.1 K by employing the PCM and the difference between the maximum and minimum temperatures in the submodule decreases in this way. The temperature differences are 0.17 K, 0.68 K, 5.80 K, and 13.33 K for volumetric heat generation rates of 6.885, 22.8, 63.97, and 200 kW/m3, respectively.