Occupational health nursing has evolved since the late 19th century and, with the inclusion of advanced practice nursing, has become essential to the health and safety of workers. A key component of the knowledge required of advanced practice occupational health nurses is an understanding of what it means for workers to be fit for duty. The definition or concept of being fit for duty varies depending on the point-of-view of the health care provider. Health care providers across all professions must have a consistent understanding of what it means to be fit for duty. Literature shows that professions and specialties that often collaborate have varying ideas about what it means to be fit for duty. These differences highlight the need for a consistent concept that can be used across professions, is holistic, and incorporates other concepts critical to all points of view. To better understand fit for duty, a concept analysis, using the Walker and Avant framework, focused on the concept of occupational functionality (OF). Occupational functionality is best defined as the qualities of being suited to serve an occupational purpose efficiently and effectively within the physical, occupational, environmental, and psychological demands of a unique work setting. This concept analysis offers an initial step in understanding fit for duty and gives health care providers a concept that can be used across disciplines.