Purpose: The purpose of this paper is to present a knowledge-sharing model that explains individual members' motivation to share knowledge (knowledge donation and knowledge collection). Design/methodology/approach: The model is based on social-constructivist theories of epistemological beliefs, learning and distributed cognition, and is organized via the mechanism of propositional control, which suggests that attitudes or beliefs largely drive one's behaviors. This paper also explores how epistemological belief systems may influence behavior processes at work. Findings: The model presented consists of five epistemological belief dimensions consistent with previous theorization about personal epistemologies. This paper demonstrates how sophisticated (as opposed to naive) beliefs on each of these five dimensions can stimulate one's intrinsic desire to engage in knowledge-sharing behaviors. Research limitations/implications: The model is constrained by the assumptions that learning takes place socially and within a specific context (in this case, the team setting), and that a great deal of knowledge sharing is preferred over little knowledge sharing. This paper adds to the understanding of workplace learning by establishing a possible new antecedent to explain the process of how team members are motivated to engage in knowledge-sharing behaviors. Practical implications: The model may be used for knowledge management and to understand ineffectiveness in teams. It also may assist in human resource functions including selecting and training team members for knowledge-intensive positions. Social implications: Epistemology affects collaborative relationships. Collaborations and associated knowledge-sharing behaviors among work team members who design and implement products for public use are imperative toward developing products free from health and safety issues. Originality/value: This paper provides a model for understanding and developing motivation to engage in individual knowledge-sharing behaviors among work team members, which is considered critical toward an organization's competitive advantage.