Recent work has shown that Proxy Mobile IPv6 (PMIPv6) is a promising mobility management protocol for its salient features, such as supporting unmodified Mobile Node (MN). However, PMIPv6 does not consider the multicast routing support. Moreover, current research mainly concerns on the multicast receiver mobility, but it is a critical and challenging issue to ensure service connectivity for mobile multicast senders, which has not been addressed well. In this paper, we propose an efficient multicast sender mobility scheme for PMIPv6 (PMIP-BT), in which the multicast data can be transmitted through the PMIPv6 tunnel and the multicast sender mobility is transparently enabled in the PMIPv6 networks. Numerical results show that the proposed scheme outperforms the current scheme in terms of signaling cost.