The purpose of this paper is to examine the factors that affect the knowledge-sharing intention and knowledge-sharing behavior in a public sector organization. A survey was conducted with 188 knowledge workers of a public-sector organization at the national level in Colombia. In this public organization significant relationships between self-efficacy and knowledge-sharing intention, subjective norms, and knowledge-sharing behavior, and between knowledge-sharing intention and knowledge-sharing behavior were found. There was a direct effect of perceived organizational support on knowledge-sharing behavior and a moderator role of perceived organizational support between the studied variables. The findings clarify how some personal variables and perceived organizational support interact in the explanation of knowledge sharing.