Transmission of datagrams to a group of hosts identified by a single destination address is Multicasting. Multicast is intended for group-oriented computing applications such as rescue teams, scientists with sharing of data and requirements for audio and video conferencing. All the multicast group members should have a group key to decrypt the datagram sent by the multicast server or source, which requires renewal for every membership view change to preserve forward and backward secrecy. Re-keying is the process in Key Management Protocol wherein a key distribution centre generates and distributes the cryptographic key during each membership event like member join or leave or transfer. The process of rekeying is required to preserve forward and backward secrecy, which induces computational, and communication overhead. In highly dynamic environments like wireless sensor networks, mobile clouds and IoTs, the members move from one area to another frequently and hence, this frequent join/leave of members in an area increases the rekey overhead. When the members become more dynamic, the rate of rekeying increases and hence the overhead increases. This paper proposes an Efficient Key Management Protocol with Predictive Rekeying Mechanism for Dynamic Networks, which reduces the effect of overhead per rekeying. The proposed mechanism reduces the frequency of rekeying by using a novel predictive rekeying, reduces the effect of mobility on the key management protocol, increases scalability, and reduces rekey overhead over other standard key establishment protocols.