The emergence of Advanced Metering Infrastructure (AMI) into the Smart Grid applications receiving significant attention by researchers of the Internet of Things (IoT) assisted smart city projects. Communication networks (WiFi/WLAN) is one of the key building blocks of AMI for information exchange. The wireless communication networks are vulnerable to various security threats that lead to problems in designing the AMI system in smart city projects. The main requirements of cyber-physical systems like AMI include confidentiality, integrity, availability, and privacy. To satisfy the requirements of cyber-physical systems, we focused on the wireless communication protocol that addresses data transmission reliability and data security with minimum power consumption and overhead. The Secure and Reliable AMI (SRAMI) protocol using the unique trust-based mechanism for reliability and lightweight cryptography mechanism for the security proposed for Wireless Sensor Network (WSN)-assisted AMI. The trust-based algorithm introduces to establish a reliable data transmission technique among two communicating entities of AMI. In this regard, next-hop selected according to trust-evaluation using parameters energy consumption, geographical distance, and bandwidth availability parameters. Furthermore, the lightweight Elliptic Curve Cryptography (ECC)-based hybrid technique introduces to satisfy the data integrity and privacy requirements in the AMI network. The performance of SRAMI evaluated using throughput, Packet Delivery Ratio (PDR), average energy consumption, delay, and communication overhead compared to state-of-art methods. The throughput and PDR improved by 5 % and 3.14 % compared to existing methods. The energy consumption, delay, and overhead reduced by 7.36 %, 12.16 %, and 17.66 % compared to existing techniques.