Paper to be presented at DRUID19 Copenhagen Business School, Copenhagen, Denmark June 19-21, 2019 Supporting Social Ventures in Institutional Voids: The Emergence of a Transnational Entrepreneurial Ecosystem for East Africa Stephan Manning University of Massachusetts, Boston Management and Marketing stephan.manning@umb.edu Stanislav Vavilov University of Massachusetts Boston College of Management stanislav.vavilov001@umb.edu Abstract This study examines how social ventures mobilize institutional support in regions characterized by resource constraints and institutional voids. Based on field studies in East Africa, we find that social ventures increasingly benefit from a transnational entrepreneurial ecosystem ? networks of organizations operating across geographic levels in support of new ventures. We find that intermediaries, such as social incubators, are critical in transnational ecosystem building by forming global-local alliances, running entrepreneurship events across levels, and linking local business and social opportunities to global development agendas. Findings inform research on social entrepreneurship and ecosystem formation in emerging economies.