Provided is a secondary battery including: an electrode assembly; a case housing the electrode assembly and having a case opening; a cap plate substantially sealing the case opening; a first terminal plate on the cap plate; a first collector terminal coupling the electrode assembly to the first terminal plate; and a seal gasket between the first collector terminal and the cap plate, wherein the first collector terminal includes: a lower terminal adjacent the electrode assembly, and an upper terminal adjacent the first terminal plate, the upper terminal including a first metal different from a second metal of the lower terminal, and contacting the lower terminal at an interface between the first metal and the second metal, and wherein the seal gasket covers at least a portion of a side surface of the interface between the first metal and the second metal.