This paper presents a performance evaluation of the adaptive network tree construction mechanism for ZigBee grid router network. ZigBee is a communication protocol for Wireless Personal Area Network (WPAN) which is built on the IEEE 802.15.4 standard. The low power characteristic of ZigBee is one of the main reasons in the selection of this protocol. An adaptive network tree construction mechanism can be implemented to support this characteristic. The mechanism is intended to form a ZigBee network topology which always minimizes the number of active ZigBee routers in a grid router topology. This mechanism will save energy consumption by turning the ZigBee routers to sleep condition when there is no end device within range to be served. A predefined routing map is used to determine the minimum number and the position of routers to be active based on the position of end devices. The performance evaluation of the mechanism is carried out using NS2 network simulator software tool. The simulation result showed that the energy consumption can be proportional to the number of active routers. In the simulation, maximum energy saving is up to 87% compared to the condition that all router always active in a 4×2 ZigBee grid router topology.