Background: Outpatient delivery of geriatric rehabilitation (GR) might contribute to preserving the accessibility and quality of GR, whilst dealing with an increasing demand for healthcare in an aging population. However, the application of outpatient GR differs between GR facilities. This study aimed to gain insight into factors influencing outpatient GR utilization. Methods: In this case study, 24 semi-structured interviews were conducted with physicians, physiotherapists, nurse practitioners, occupational therapists, and managers in GR. Interviews were transcribed and analyzed using summative content analysis. Results: Various patient-related barriers for using outpatient GR were mentioned including lacking social support and limited capacities and self-management skills. Additionally, professional-related barriers included a lack of awareness and consensus among care professionals regarding the possibilities and potential advantages of outpatient GR. Yet, most perceived barriers were related to efficiency and organization of outpatient GR (e.g., reimbursement system, lacking practical guidance). Still, most participants were in favor of increasing outpatient GR because of expected advantages for patients, GR organizations, and society. Conclusions: Despite experienced barriers, there seems to be agreement on the need to increase outpatient GR application. It is recommended to use the present findings to develop and evaluate new ways of organizing and reimbursing outpatient GR.