This paper examines the feasibility and suitability of applying conventional microfinance impact assessment (MIA) methodologies in the EU-15 context. Drawing on the authors’ experience conducting a large-scale microfinance impact study in the UK, the research evaluates the challenges of using longitudinal surveys, control groups, and experimental approaches that are commonly employed in developing countries. The findings indicate that such methodologies face significant limitations in industrialized countries due to the relatively small client bases of microfinance institutions, difficulties in recruiting and retaining financially excluded participants, and high survey refusal and attrition rates. Additionally, identifying appropriate control groups is complicated by the widespread presence of welfare programs and financial inclusion initiatives that may influence outcomes. The study argues that these contextual factors make it difficult to isolate the effects of microfinance using traditional impact assessment methods. Consequently, the authors call for the development of a new methodological framework better suited to the realities of the European microfinance sector, offering valuable insights for both researchers and practitioners seeking to evaluate microfinance impact more effectively.