Social investment in East Africa is emerging rapidly with significant potential to advance sustainable development goals. It is crucial in funding various development areas such as financial inclusion, poverty eradication, health, education, and sustainable energy. This study uses a mixed methods approach to analyze the social investment landscape in East Africa, focusing on Kenya, Uganda, and Tanzania. By reviewing literature, secondary data, and a survey of social investors, the study applies a basic social investment market framework to identify key players in the supply and demand sectors. Findings indicate a mismatch between the supply of investment capital and the demand from organizations, with demand surpassing supply. The study also examines challenges faced by social investment participants and offers recommendations to enhance the scale of social investment in the region.