Knowledge is essential for the functioning of every social system, especially for professionals in knowledge-intensive organisations. Since individuals do not possess all the work-related knowledge that they require, they turn to others in search for that knowledge. While prior research has mainly focused on antecedents and consequences of knowledge sharing and understanding why people do not share knowledge, less is known why people provide knowledge, and what conditions trigger voluntary engagement in knowledge sharing. Our article addresses this gap by proposing a multi-level framework for voluntary engagement in knowledge sharing: individual, relational, group, and informational. We provide illustrations from a particular knowledge-intensive community, DNA forensic scientists who work at public laboratories. (Contains 5 figures and 1 note.)