While the importance of knowledge management in organizations and its benefits as innovative powers and a competitive edge is a widely accepted notion in our field of research, it lacks contributions that focus on how knowledge management can be performed in a sustainable way. If we rely so strongly on knowledge management, we should strive for it that current knowledge practices respect both present and future knowledge demands. This paper aims to uncover how organizations can stimulate sustainable knowledge management, meaning the extent to which the organization is capable to track and adapt to changes, internally and in its external environment, by seeking its enablers. While it is clear now that an important part of knowledge in organizations resides in the informal networks, we use the concept of social capital as a measure for informal networks in organizations. By assessing 50 Dutch knowledge-intensive organizations, we seek to reveal to what extent the existence of social capital is an enabler for a set of best practices in knowledge management (known as New Knowledge Management) of which its practice is regarded as sustainable knowledge management.