Wireless sensor networks (WSNs), an emerging large-scale network system can be embedded for any application. The designers of wireless sensor network have to consider the quality of service agreements from a user perspective. The WSN is very rapid in dynamic changing topology and has less energy, computing and communication resources.The network design has to fulfill the QoS parameters like reliability, timeliness and lifetime of the network. In wireless sensor network, when two nodes transmit messages through a common visible node and collision occurs between these nodes is refers to as hidden node problem. Many researchers have reviewed the hidden node problem affecting the throughput and lifetime of the network. This paper proposed Inter-Cluster Grouping Mechanism (ICGM) to handles the problem of inter-cluster grouping and hidden node for the improvement of Quality of Service (QoS) factors in WSN. The performance of WSN degrades due to the occurrence of inter-cluster interference caused by different grouping mechanism as imposed in different clusters. The proposed mechanism (ICGM) overcome the problem of inter-cluster interference and increases the QoS in WSNs.