Energy harvesting (EH) is considered the key enabling technology for mass deployment of Internet-of-Things (IoT) devices. Efficient EH techniques eliminate the needs for frequent energy source replacement, thus offering a near perpetual network operating environment. Advances in the EH techniques have shifted the design paradigm of routing protocols for energy-harvesting wireless sensor network based IoT applications from “energy-aware” to “energy-harvesting-aware” . This paper aims to design an energy-harvesting-aware routing protocol for heterogeneous IoT networks in the presence of ambient energy sources. We propose a new routing algorithm energy-harvesting-aware routing algorithm (EHARA), which is further enhanced by integrating a new parameter called “energy back-off” . Combining with different energy harvesting techniques, the proposed algorithm improves the lifetime of the nodes and the network’s quality-of-service (QoS) under variable traffic load and energy availability conditions. This work also investigates the system performance metrics for different energy harvesting conditions. Performance results demonstrate that the proposed EHARA significantly improves energy efficiency while satisfying the QoS requirements of distributed IoT networks in comparison with existing routing protocols.