Software-Defined Networking (SDN) has been introduced to Wireless Sensor Networks (WSNs) to achieve centralized control and flexible network management. In Software-Defined Wireless Sensor Networks (SDWSNs), security and energy are two critical issues. However, few studies address these two aspects simultaneously. In this paper, we propose an Energy-efficient Trust Management and Routing Mechanism (ETMRM) for SDWSNs to handle the malicious forwarding attacks, such as selective forwarding attack and new-flow attack. In the ETMRM, we firstly extend the SensorFlow tables to realize a light-weight trust monitoring and evaluation scheme at the node level, and propose a centralized trust management scheme at the controller level to detect and isolate the malicious nodes based on the trust information collected from sensor nodes. Secondly, we present an energy-efficient report message aggregating scheme for aggregation points’ selection to save energy and ensure the transmission of control traffic. Thirdly, we present a trust routing mechanism jointly considering the node’s residual energy and trust level to guarantee the transmission of data traffic. The experimental results show that the proposed architecture detects and responds to the internal network attacks, such as Greyhole, Blackhole, new-flow attacks, efficiently. Compared with the related work SDN-WISE, ETMRM improves the packet delivery ratio, reduces and balances the energy consumption, prolongs the network lifetime, and suffers lower control overhead.