The Nigerian business environment is characterised by persistent structural and governance impediments that constrain enterprise growth and economic development. Existing analyses often treat these challenges in isolation, lacking an integrated diagnostic tool for practitioners and policymakers. This paper develops and presents a novel diagnostic framework to systematically identify, categorise, and analyse the interconnected structural and governance challenges faced by businesses operating within the country. The research employs a multi-method design, synthesising data from a systematic review of policy documents and extant literature with insights from semi-structured interviews conducted with a purposive sample of senior enterprise executives and regulatory officials. Analysis reveals that infrastructural deficiencies, particularly in power supply and logistics, are perceived as the most binding constraint, directly cited by over 70% of interviewees as their primary operational bottleneck. These structural issues are compounded by opaque regulatory governance, creating a complex nexus of barriers. The study concludes that the nation's business challenges are deeply systemic and mutually reinforcing, necessitating coordinated rather than piecemeal interventions. The proposed framework effectively captures this interconnectivity. It is recommended that regulators adopt the diagnostic framework for holistic policy formulation. Business support organisations should utilise it for targeted advocacy and to guide enterprise risk management strategies. business environment, diagnostic framework, governance, structural constraints, Nigeria This paper's primary contribution is the introduction of a novel, integrated diagnostic framework that maps the causal relationships between distinct structural and governance barriers, offering a practical tool for strategic analysis and policy design.