Since security plays an important role in several ZigBee applications, such as Smart Energy and medical sensor applications, ZigBee Specification includes various security mechanisms to protect ZigBee frames and infrastructure. Among them, the Join and Leave operations of ZigBee are investigated in this paper. The current Join-Leave operation is protected by the network key (a kind of group key). We claim it is not adequate to employ the network key for such purpose, and propose a new Join-Leave operation protected by the application link key (a kind of pairwise key), which is based on a more efficient key management scheme than that of ZigBee. Hence, the original Join operation consists of a total of 12 command frames, while the new Join operation consists of only 6 command frames. In particular, the security of the proposed Join-Leave operation is equivalent to or better than that of the original Join-Leave operation. The new Join-Leave operation is extensively analyzed in terms of security and efficiency, and compared with the original Join-Leave operation of ZigBee.