The Problem Agency theory has been empirically studied in other fields of study such as economics, political science, sociology, and management. Although a proposal for inclusion of agency theory to test training and development outcomes was made in human resource development (HRD)-related publications, little research has been conducted and published in HRD-related literature. The Solution This review of agency theory offers a description of the elements and factors associated with the principal–agent relationship that have been theorized and empirically tested in other fields of study. Much of the theoretical implications are transferable to HRD. The principal–agent relationship should be empirically tested in HRD situations and interpreted through an HRD lens. The Stakeholders The review of the principal–agent relationship in other fields is expected to benefit HRD researchers, practitioners, principals, and agents in organizations by providing insight into the orientation, elements, and influence of principal–agent relationships.