Eighty-four self-identified healthcare or service professionals (71% professional organizers, 19% healthcare workers, 10% social service workers) completed an internet survey of their experiences with, and attitudes toward, one hoarding and one non-hoarding client. When working with hoarding clients, professionals described feeling increasingly frustrated and irritated, reported poorer working alliance, and harbored greater patient rejection attitudes than when working with non-hoarding clients. Hoarding clients were described as having less insight and understanding, with a higher frequency of intervention–interfering behaviors, and diminished adherence. Working alliance and patient rejection attitudes were significantly predicted by clients' intra- and inter-session behaviors, particularly difficulty answering questions appropriately, poor insight, arguing, and lack of active participation in treatment. Recommendations for treatment modifications are intended to improve working alliance and decrease patient rejection attitudes for professionals working with hoarding clients.