This disclosure relates to a battery assembly of an electrified vehicle, and in particular to a battery pack with a vent gas passageway. An example battery assembly includes a battery array having a plurality of battery cells. Each of the battery cells includes a vent configured to release vent gas from a respective one of the battery cells. Further, the battery assembly includes an enclosure assembly surrounding the battery array, and a vent gas passageway within the enclosure assembly. The vent gas passageway includes a plurality of inlet ports, and each of the inlet ports is substantially aligned with a respective one of the vents.