The Smart Grid is expected to greatly enhance the efficiency and reliability of today’s elderly electricity grid by employing advanced information and communication technologies. In smart grid, the IoT-enabled Wireless Sensor Networks (WSNs) are considered as promising solutions due to their advantages, such as cable replacement, ease of deployment, flexibility, and cost reduction. IoWSNs can efficiently integrate, control, and monitor geographically DER in the smart grid. However, the inherent weakness of IoWSN has exposed critical power facilities to numerous security threats resulting in power grid operational failures and loss of synchronization. This perational failure may damage critical power system components which may interrupt the power supply and make the system unstable resulting high financial penalties. To address these issues, this research proposes a Lightweight Private Blockchain based Secure Communication Framework (BCF) in IoWSNs for efficient and reliable data transmission in the DER applications. Theoretical analysis and extensive simulations using network simulation called RTDS will be carried out to verify the effectiveness of the proposed scheme for DERs in the SG.