Social innovation is a useful mechanism to address unmet needs in local societies and tackle wicked problems through innovative products and services. Policymakers and practitioners have increasingly become interested in effective policies and strategies for facilitating social innovation to deliver sustainable development; however, a lack of coherent analytical framework persists. To address this gap, we propose the Social Innovation System framework, by adapting the Technological Innovation Systems approach widely used in innovation management and policy. Providing a holistic and comprehensive perspective to explore complex interactions among different actors and institutions involved in social innovation, our framework allows more systematic understanding of the development of social entrepreneurship and relevant ecosystems. We employ this framework to analyze social innovation ecosystems in South Korea and Singapore. The results indicate systemic challenges to overcome owing to the collective and interactive nature of social innovation.