Purpose Knowledge theft represents a significant barrier to knowledge management initiatives. Yet, despite recent attention in the popular press, little is known about the phenomenon overall. This study aims to fill this gap through the development of a reliable and valid measure of knowledge theft. Design/methodology/approach Using over 1,500 participants in seven separate samples, the authors engage in a process of item generation and establish the construct, convergent and discriminant validity of a knowledge theft scale. Findings The results demonstrate that knowledge theft is distinct from other forms of interpersonal deviance, such as social undermining and interpersonal aggression. Additionally, employees who have experienced knowledge theft report increased intentions to engage in knowledge hiding, defensive silence and other counterproductive work behaviors that might impede knowledge management efforts in organizations. Originality/value To the best of the authors’ knowledge, this research represents the first attempt to systematically study knowledge theft in organizations and demonstrates the ubiquity of the phenomenon. Further, the newly developed knowledge theft scale allows future research in this area to uncover the impact of knowledge theft on victims, witnesses, perpetrators, and organizations.