A battery pack includes a bare cell and a protection circuit assembly electrically connected to the bare cell. The protection circuit assembly includes a protection circuit board on which a protection module, a PTC thermistor, an external connection terminal, a first connection terminal and a second connection terminal are mounted. A first lead plate and a second lead plate are in contact with the first connection terminal and the second connection terminal, respectively. The protection circuit board defines opposite lateral edges and a first groove in each of the opposite lateral edges, and the first lead plate is exposed through the first groove.