Business development in sub-Saharan Africa is often constrained by institutional voids—the absence of market-supporting institutions. The literature lacks fine-grained diagnostic tools that account for entrepreneurial agency in navigating these voids, particularly in smaller economies. This paper develops and presents a novel diagnostic framework to analyse how entrepreneurs perceive and actively respond to institutional voids, with the objective of identifying viable strategic pathways for enterprise growth. The research employs a longitudinal, qualitative case study methodology, analysing data from in-depth interviews with founders and senior managers of 22 small and medium-sized enterprises, supplemented by archival analysis of policy documents and firm records. Entrepreneurs predominantly employ bridging and buffering strategies, with over 70% of cases relying on informal networks to substitute for missing formal institutions. A key theme was the strategic internalisation of functions, such as self-provisioning logistics, to circumvent infrastructural gaps. Entrepreneurial agency is a critical mediator of institutional voids, with strategic responses forming predictable patterns that can be systematically categorised to inform both managerial practice and policy design. Policymakers should focus on co-creating solutions with the private sector that formalise effective informal practices. Business development programmes must train entrepreneurs in institutional diagnostics and strategic response formulation. institutional voids, entrepreneurial agency, diagnostic framework, business development, informal institutions, strategy This paper provides a novel, practitioner-oriented diagnostic framework that integrates institutional theory with strategic management, offering a structured tool for analysing firm-level responses to macro-level institutional deficiencies.