The increasing adoption of unmanned aerial vehicles (UAVs) has raised significant security concerns, including privacy breaches, network flooding attacks, identity spoofing attacks, and eavesdropping and interception attacks. To overcome these challenges, this paper introduces a novel blockchain-enabled authenticated key agreement mechanism for securing UAV communications. The proposed protocol ensures data integrity, confidentiality, and authentication while mitigating common security threats. The protocol's security has been rigorously investigated using the random oracle model and the AVISPA tool, covering various adversarial scenarios. Furthermore, a mathematical security analysis confirms its resilience against major attacks. A qualified performance assessment highlights that the proposed mechanism achieves an improvement in efficiency over the protocol of the related protocols, along with enhanced communication and computation performance. The results confirm that the proposed solution offers a secure and efficient approach to UAV network authentication. This research contributes to strengthening UAV security by integrating blockchain technology, making it a robust solution for protecting UAV networks from potential cyber threats.