Multicast routing that meets multiple quality of service constraints is important for supporting multimedia com-munications in the Internet of Things (IoT). Existing multicast routing technologies for IoT mainly focus on ad hoc sensor net-working scenarios; thus, are not responsive and robust enough for supporting multimedia applications in an IoT environment. In order to tackle the challenging problem of multicast routing for multimedia communications in IoT, in this paper, we pro-pose two algorithms for the establishing multicast routing tree for multimedia data transmissions. The proposed algorithms leverage an entropy-based process to aggregate all weights into a comprehensive metric, and then uses it to search a multicast tree on the basis of the spanning tree and shortest path tree algorithms. We conduct theoretical analysis and extensive simulations for evaluating the proposed algorithms. Both analytical and experimental results demonstrate that one of the proposed algorithms is more efficient than a representative multiconstrained multicast routing algorithm in terms of both speed and accuracy; thus, is able to support multimedia communications in an IoT environ-ment. We believe that our results are able to provide in-depth insight into the multicast routing algorithm design for multimedia communications in IoT.