This article investigates how a start-up foundation can build its organisational social capital, meaning a network of strategic partnerships with other organisations based on trust relationships, in order to fulfil its mission. Based on a case study analysis of Fondazione Welfare Ambrosiano - an Italian foundation created in partnership with private organisations and local public institutions - we explored whether and how some characteristics of the social capital of the foundation’s members contributed to the organisational social capital. By applying Nahapiet and Ghoshal’s (1998) social capital framework, we discovered that the social capital configuration of the founders and staff, linked to some characteristics of the foundation, had d...