Knowledge sharing is an employee behavior, critical to organizational success in knowledge‐intensive work environments. This study set out to empirically test the model of knowledge‐sharing motivation designed and presented in this journal by Gagné (2009). The model combines two established behavioral theories, the theory of planned behavior and self‐determination theory, and connects various human resource practices to it. This prospective survey study ( n = 200) in a large expert organization employed structural equation modeling. The results mainly supported the proposed model, with attitudes, autonomous motivation, and sharing norms predicting knowledge‐sharing intentions ( R2 = .69), which predicted knowledge‐sharing behavior ( R2 = .42). We also identified potential ways to modify the model to better suit typical knowledge‐sharing contexts. Implications for practice, with the emphasis on how our findings can benefit and be used by human resource management, are discussed. © 2016 Wiley Periodicals, Inc.