Social capital is put forward as a suitable theoretical framework to explain knowledge sharing mechanisms in organizations. The aim of this paper is to summarize lessons learned from different contexts where the social capital dimensions have been used to explain information and knowledge sharing. The contexts studied are mainly within business organizations, virtual worlds, and higher education. The dimensions of social capital have been found useful when exploring knowledge sharing practices. The studies illuminate important aspects on how the combination of structures, relations and contents support sharing. The different cases also underline the importance of the contextual dimension, the role of the social capital dimensions are focused differently depending on context.