This application relates to the technical field of energy storage devices, and in particular, to an upper cover assembly and a battery pack. The upper cover assembly includes: an upper cover body, including a top plate and a side plate connected to an outer periphery of the top plate, wherein an exhaust vent is provided in the side plate; and an exhaust unit, including a first exhaust unit and a second exhaust unit that communicates with each other, wherein the first exhaust unit is disposed on the top plate, the second exhaust unit is disposed on the side plate, and the first exhaust unit communicates with the exhaust vent through the second exhaust unit. The upper cover assembly provided in this application allows gas (in battery cells) to be quickly discharged from the first exhaust unit and the second exhaust unit to the exhaust vent.