Blockchain ecosystems are increasingly expanding beyond single-organization boundaries, enabling multiple stakeholders such as governments, private enterprises, NGOs, regulators, and citizens to collaborate on trusted digital platforms. However, the security challenges emerging from multi-stakeholder participation are more complex than traditional blockchain environments, due to conflicting incentives, heterogeneous infrastructures, and regulatory variations. This study aims to develop a comprehensive security framework tailored for multi-stakeholder blockchain ecosystems through a synthesis of existing literature, architecture analysis, and threat modeling. The proposed “MS-BSF Model” outlines five security layers—governance, identity, consensus, data, and operational security—supported by cross-layer trust and compliance mechanisms. The study provides theoretical contributions, practical guidelines, and future research agendas.