Traditional routing protocols in wireless mesh networks establish a single data path between a source and a destination. However, the performance suffers from degradation and instability due to variation of wireless links and interference. Opportunistic routing has been proposed to overcome the problem by exploiting the broadcast nature of wireless links and multiple forwarders. Current opportunistic routing protocols with network coding improve the system performance but suffer from redundant packet transmissions because a source stops transmitting packets in the same segment until it receives an ACK message from the destination. In this paper, we propose a pipelined opportunistic routing protocol with network coding (PipelineOR) in which segments are transmitted in a pipelined manner. A source is allowed to send packets in the next segment without waiting for the ACK message from the destination. In addition, we present two mechanisms, namely ETX-based mechanism and DCounter-based mechanism, to suppress forwarders to transmit redundant packets. The simulation results show that the proposed PipelineOR outperforms MORE  and CodeOR  in terms of transmission time.