Non-governmental organisations (NGOs) that focus on humanitarianism, such as the Red Cross, provide services that make the world a better place. To do so, they are highly dependent on a network that generates goodwill, volunteers, and donations. Social Networking Sites (SNS) are a vital channel for NGOs to pursue their organisational objectives. However, how NGOs utilise SNS to tap into resources for social action is insufficiently understood. In this paper, we investigate how the German Red Cross builds and fosters online social capital via SNS. We conducted semi-structured interviews with five SNS experts from regional units of the German Red Cross and analysed their corresponding Twitter and Facebook profiles. Our findings help identify crucial areas of social capital management via SNS for practitioners in the non-profit sector. Moreover, our research contributes to the conceptualisation of organisational online social capital by classifying SNS constituents with respect to structural, relational, and cognitive dimensions