Collaborative Networked Organizations are being considered a response to the economic market pressures. Some research projects try to identify the key factors that enable the growth and survival of these collaborative networks. One strategy is to create Virtual Organization Breeding Environments in order to prepare organizations and persons to rapidly respond to a collaboration opportunity. In those breeding environments is possible to develop endogenous resources that permit collaborative practices, like social capital. The present paper discusses the importance of Social Capital and its relationship with Knowledge Management for Virtual Organization Breeding Environments. Knowledge is created during the processes of collaborative networks that rarely are documented and reused. Implementing an effective Knowledge Management method will motivate to increase Social Capital. The present work points out that knowledge sharing is important to develop Social Capital in three Brazilian collaborative networks called VIRFEBRAS, APROVALE and APROBELO.