Schizoaffective disorder has routinely exhibited poor outcomes related to diagnostic accuracy and reliability. These pitfalls have been linked to the conceptual nature of Schizoaffective Disorder’s combined psychotic and affective symptoms. Clinicians likely perceive the psychotic components of Schizoaffective Disorder as more severe than the affective symptoms, and have demonstrated a bias toward misdiagnosing Schizoaffective Disorder as Schizophrenia. Thus, the present study sought to examine the clinical conceptualizations of Schizoaffective Disorder compared to Schizophrenia, Bipolar Disorder with psychotic features, and Major Depressive Disorder with psychotic features. The participants were clinicians recruited via email and randomly assigned to either select symptoms from a predetermined criteria list (Recognition group) or to freely list features of the disorders based on their own mental representations (Unprompted group). Participants’ conceptualizations of Schizoaffective Disorder were not entirely congruent with DSM-5 criteria; they conceptualized it as less psychotic than Schizophrenia and less affective than the two mood disorder tasks. Schizoaffective Disorder exhibited the lowest proportion of accurate endorsements, and Schizophrenia had the highest proportion. We hypothesized that Schizoaffective Disorder would have the most overextension endorsements because of its fuzzy boundaries, but Schizophrenia had the highest instead. The Recognition Group outperformed the Unprompted Group overall, which can be explained by the availability heuristic. This study’s findings support the notion that Schizoaffective Disorder’s poor diagnostic outcomes are possibly related to clinicians’ conceptualization of the construct, or that its current diagnostic formulation is not congruent with what clinicians observe in clinical settings.