A battery pack providing power to a portable electronic device is disclosed which inhibits electromagnetic waves generated by the battery pack from interfering with the portable electronic device. The portable electronic device may include a radiofrequency (RF) circuit including a transceiver. The battery pack may include a battery cell and a protection circuit module (PCM) which operates to prevent the battery cell from overcharge/overdischarge and overheating. The PCM may include a substrate and a protection device mounted to the substrate. Electromagnetic waves generated when the protection device operates are shielded from the portable electronic device by a shielding layer formed on the substrate of the PCM. The substrate may include a plurality of circuit layers, each including a circuit layer, with the circuit layers in electrical communication with one another. A shielding pattern is formed on at least one of the circuit layers.