IEEE 802.15.4 standard is designed to achieve low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). For the sake of reducing the power consumption, IEEE 802.15.4 uses the modified CSMA/CA protocol and does not have the hidden node protection mechanism, such as RTS/CTS mechanism. Previous studies indicated that the probability of any two nodes in an infrastructure network unheard of each other is around 41%. Therefore, the hidden node problem (HNP) results in inefficient data transmission and serious power consumption issues in WPAN. In this paper, we propose an efficient grouping strategy, which is performed during node joining, to completely avoid the HNP. We allocate the hidden nodes into different groups to transmit their frame, and the new joining node does not affect the existent groups. Based on the grouping result, the proposed scheme partitions the time of a superframe into several subperiods, and the length of subperiod depends on the number of hidden nodes in a group. Simulation results show that the proposed scheme not only avoids the HNP but also outperforms the performance of IEEE 802.15.4 standard.