This paper is focussed on the development of an exploratory integrated perspective to understand and measure Social Innovation Ecosystems through the notion of Social Innovation Regime. This concept builds upon the interrelation between socioeconomic contexts of SI (meso–macro levels) and intra/inter-organizational dynamics (micro level), where SIs are developing. That is to say, the ways in which the social economy and social organizations are connected to a broader SI Ecosystem where the socioeconomic contexts surrounding National Welfare Regime try to answer to the policy and market failures that have an impact on regional vulnerability rates. This article suggests the hypothesis that there is an interrelation between the strength of Welfare Regimes and Social Innovation Ecosystems, at a time where Social Policies and Welfare States all over the world are weakened or in crisis, opening the door to social innovation. This paper describes this connection through the notion of Social Innovation Regime, proposing an interesting exploratory framework to explore the socio-structural factors through which a country or region presents a set of vulnerabilities which can transform into unattended social problems. Finally, this analysis can contribute to the methodologies on SI measurement and impact by determining the regional vulnerability rate – social, economic, institutional, environmental – inside welfare regimes.