<p>Software Defined Networking (SDN) enhances network programmability and management by decoupling control and data planes. However, this logically centralized control plane introduces scalability issues and security vulnerabilities. In multi-domain SDN architectures malicious entities can compromise controllers to inject false flow rules, disrupting network integrity. Existing solutions often rely on static cryptographic authorizations, failing to monitor the real-time operational integrity of controllers. To address these limitations, this paper proposes an enhanced blockchain-based control layer security framework in multi-domain SDN (EBCS-SDN). The framework introduced a dynamic trust scoring model, an optimized dual-phase controller authentication mechanism and a decentralized behavioral-deviation hijack detection system to ensure continuous controller accountability. The empirical evaluations in a simulated multi-domain SDN environment demonstrated significant performance and security improvements over existing baselines models Voting-based, Proof-of-work (PoW)-based, DLCA_R_P, and BCS. Simulations in an emulated environment show that the proposed framework optimally reduces controller authentication latency by up to 75% and achieves a hijack detection accuracy of 96.78%. Under these simulated proof-of-concept conditions, the system demonstrated a post-attack throughput of 980 Mbps with detection and isolation times under 1.2&#xa0;s. The proposed framework optimized the CPU utilization at full network nodes. Ultimately, the proposed system provides a scalable, computationally lightweight, and operationally resilient security foundation for SDN deployments.</p>