In my dissertation, I explore the phenomenon of workplace impostor thoughts, defined as the belief that others hold an overly positive view of one’s talent or abilities at work. Having workplace impostor thoughts may be far from rare. Yet, the phenomenon remains underexplored by management and organizational behavior scholars. As a result, numerous fundamental questions remain unanswered concerning the phenomenon’s conceptual bounds, workplace antecedents, mechanisms, and intrapersonal as well as interpersonal consequences. For example, little consensus exists as to the phenomenon’s precise definition. Furthermore, the work that does exist has overly favored the drawbacks without considering its benefits. Indeed, there are hints within existing and related work that having workplace impostor thoughts may not be as pernicious as it is portrayed. Accordingly, using both qualitative and quantitative methods, I clarify what impostor thoughts are, where they come from, how they affect the self, and how they affect others. I specifically focus on unearthing the benefits that emanate from having workplace impostor thoughts with the aim of presenting a more complete picture of this phenomenon. In Chapter 1, I develop and test a theoretical model linking workplace impostor thoughts to two types of performance, task and interpersonal. As part of this effort, I inductively flesh out the construct of workplace impostor thoughts using 377 news articles and blog posts as well as develop and validate a self-report measure of impostor thoughts using seven different lab and field samples. In Chapter 2, I explore how workplace impostor thoughts impact one’s sense of mastery at work. Specifically, I outline a myriad of pathways—sometimes competing—that define the complicated relationship between having workplace impostor thoughts and job mastery. I conclude each chapter by elucidating how my theory and empirical work extend and uncover a number of surprising insights for the literatures on workplace impostor thoughts as well as for the theories and related literatures upon which I draw. Finally, I close by discussing how the topic of workplace impostor thoughts presents opportunities ripe for future inquiry.