The Internet of Vehicular Things (IoVT) field is expanding rapidly through the application of advanced technologies that enable the connection of vehicles, infrastructure , and other entities to the Internet. In addition to generating valuable data-driven insights, this development offers many advantages, such as enhancing safety, efficiency, convenience, and delivering personalized services. IoVT data is sensitive and requires secure storage and transmission, and if this information falls into the wrong hands, it could be misused for malicious purposes such as theft, fraud, or stalking. An unauthorized access to IoVT data has the potential to jeopardize the safety and security of vehicles and their passengers. Therefore, it is vital to establish a robust security mechanism to guarantee secure communication, ensure vehicle safety and integrity, facilitate efficient traffic management, provide emergency services, protect privacy and data, prevent unauthorized access, and to ensure compliance with regulations. To address the security requirements of IoVT, this research presents an innovative group-based authentication & key agreement protocol designed explicitly for IoVT, and strives to achieve the core security objectives within the 5G networks. The proposed protocol successfully fulfills crucial security objectives in IoVT, including subscriber privacy, key confirmation , authentication & key agreement, perfect forward/backward key secrecy, and session unlinkability. The security claims of the protocol underwent thorough examination using the AVISPA tool and BAN logic, confirming its ability to withstand diverse cryptographic attacks. Additionally, a mathematical investigation has affirmed the protocol’s suitability for IoVT devices, as it successfully achieves its objectives while minimizing signaling overhead, bandwidth usage, and computational burden.