Over the past four decades, group-based microfinance programs have spread rapidly throughout south Asia, sub-Saharan Africa and Latin America. Recent evaluations of the programs have identified social capital as a common byproduct of frequent association by members, increasing trust, belonging and normative influence. Concurrently, social capital is increasingly recognized as an important health determinant. We present an overview of a program intervention operating in Kenya that utilizes a microfinance approach to produce social capital, and seeks to leverage that social capital to promote health at three levels-the village, group, and individual. A theory of change is presented for each of these three levels, demonstrating conceptually and with program examples how social capital can be applied to promote health. Related social theories and approaches, further research and program directions are given for each of the three levels. We identify potential to improve a broad range of health outcomes through this innovative model, which requires engagement with health promotion researchers and planners in low- and middle-income countries for further refinement and validation.