Clinicians’ judgments about clients can be influenced by the causal context (e.g., life events) preceding behavioral symptoms. However, it is unclear whether this influence extends to diagnosis judgments. In diagnosing Posttraumatic Stress Disorder (PTSD), traumatic event context must be present, and severe immediate reaction context was formerly required for many years. In a vignette study, we systematically examined whether event and reaction severity influence clinicians’ open-ended diagnoses of PTSD behaviors, Major Depressive Disorder (MDD) behaviors, and nondisordered behaviors. Clinicians made more diagnoses of PTSD for all three types of behaviors (PTSD, MDD, distressed) given a traumatic event than a mildly stressful event but simultaneously found the behaviors to be less abnormal. We found no evidence that reaction context influenced diagnoses. Future directions and the role of causal context in clinical diagnosis are discussed.