A battery pack includes: a battery cell having a cell tab extending outwardly; a protection circuit module electrically connected to the cell tab to prevent over-charging and over-discharging of the battery cell; and a module case accommodating the protection circuit module and mounted on the battery cell, wherein the module case includes a first region, a second region positioned on the first region, and a third region extending from the first region through the second region, and the protection circuit module is accommodated in a cavity provided between the first region and the second region.