This article addresses the question of whether institutional frameworks matter in the capital structure of microfinance institutions. We studied a sample of 292 MFIs between 2004 and 2009. Our findings suggest that creditor rights, a country's legal tradition, and the level of financial sector development are significantly related to MFIs' level of external finance. Furthermore, the positive relationship between banking sector development and borrowings enables us to conclude that the microfinance sector and the formal banking sector are complementary. In addition, a split sample technique is used in order to assess the external validity of the model. Findings from this cross-validation strengthen the results obtained from the whole sample and indicate that our model seems to predict well the effect of institutional variables on the capital structure of MFIs.