Theories on social capital and their effects on social entrepreneurship has mainly underlined the power of social capital to generate enterprises and to foster good relations between third sector organizations and public sector. This paper proposes a different perspective to consider role in build social capital of a third sector enterprise: multistakeholder social cooperative are seen, at the same time, as social capital result, creators, and incubators. To represent this perspective we’ll use a qualitative system dynamic approach in which social capital is measured throw some proxy. Italian Social cooperatives has become during last twenty years main producers of social welfare service: some of them adopt a multistakeholder governance model and declare themselves as “community enterprise” choosing to represent “general interest of the community and integrating in an enterprise activity”. Sometimes they operate integrating disadvantaged people in work activities,these are work integration social enterprise, some of them, as effect of local authorities contracts. are involved in managing public services. Often these typology of social enterprises are engaged by people who come from third sector organizations and this is the way in which they continue their personal commitment in social enterprises. These people bring their relation and these “personal weak ties” are fundamental in developing cooperatives: so social capital developed in other third sector entities is transferred in multistakeholder cooperative. Cooperation of voluntary, customers, community leaders and third sector local organizations are fundamental to establish trust relations between cooperative and public local authorities. These relations help cooperatives to have long term contracts with local authorities contract as provider of social services and make them possible to innovate the services, developing experiences and management models and exchanging them with the public officers. The long-term relations and the organizational relations that linked social cooperatives and public organizations contribute to create and renovate social capital. In this way multistakeholder cooperatives originated by social capital developed in third sector organizations produce new social capital within the cooperatives and between cooperatives (entrepreneurial components of third sector) and public sector. In their entrepreneurial life cooperatives has to contrast the “working drift” in which only workers remain as members of the cooperative while others stakeholders (volunteers, customer, local social leaders) don’t continue their participation in cooperative. These people different from workers are (stake)holders of “weak ties” fundamental to make a worker’s cooperative an authentic social multistakeholders cooperative. To maintain the multistakeholders governance, and the relations with third sector and civil society, social cooperative has to reinforce participation and dialogue with civil society through continue effort of inclusion of people bringing social proposal. We try to represent these process in a system dynamic model, measuring social capital created by social cooperatives through some proxy as number of volunteers and deep cooperation with public institution. Using a reverse-engineering approach we can individuate the determinants of the creation of social capital and so give support to governance that create social capital. In this way, relations between third sector, public sector are at the same time in a social multistakeholder enterprise resulting and building social capital.