Social entrepreneurship has become an important mechanism for addressing persistent socioeconomic and environmental challenges, particularly in emerging economies where formal institutions and markets may be unable to meet critical social needs. However, the ability of social enterprises to demonstrate and scale their impact is frequently constrained by institutional deficiencies and weak impact-measurement systems. This study examined the relationships among institutional voids, impact measurement capability, funding access, and social impact among 650 social enterprises in Nigeria. The enterprises operated across health, education, agriculture, water, sanitation and hygiene (WASH), and energy sectors. A quantitative cross-sectional survey design was adopted, and the principal constructs were measured using multi-item scales adapted from established institutional, stakeholder, and social-impact measurement frameworks. The proposed model was analysed using Partial Least Squares Structural Equation Modelling and sequential mediation analysis with 5,000 bootstrap resamples. The available structural model indicates that institutional voids negatively influence impact measurement capability, while impact measurement capability positively influences funding access. Funding access, in turn, positively influences social impact. The sequential indirect pathway from institutional voids through impact measurement capability and funding access to social impact was also significant, indicating that institutional deficiencies may diminish social outcomes by weakening enterprises' capacity to generate credible impact evidence and mobilise external financial resources. The study contributes to social entrepreneurship and institutional-void scholarship by positioning impact measurement capability as a strategic organisational resource capable of reducing information asymmetry, strengthening legitimacy, and facilitating resource mobilisation. The findings underscore the need for improved social-impact data infrastructure, clearer regulatory support, investment-readiness programmes, capacity building, and financing mechanisms tailored to Nigerian social enterprises.