The present disclosure relates to a casing for a battery pack and a battery pack. The casing has a receiving space and an opening in communication with the receiving space, the receiving space is formed by a wall portion of the casing, and the wall portion is formed from two or more stacked base plates, between which a plurality of cavities are formed, wherein an island is disposed within the cavity. By disposing islands in the plurality of cavities, the casing provided by the present disclosure not only can improve the structural strength of the casing and of the cavities, but also can change the flow capacity and flow rate of the fluid in the cavities, which can make the temperature distribution of the casing more uniform, increase the heat exchange efficiency of the battery assembly, and further improve the thermal management of the battery pack.