This article describes a diagrammatic clinical tool to be used when formulating cases in eye movement desensitization and reprocessing (EMDR) therapy. Based on the Adaptive Information Processing (AIP) model, the EMDR Case Formulation Tool is a way of illustrating psychological difficulties, mapping out the relationships between six key elements: unprocessed traumatic experiences, triggers, intrusions, negative beliefs, and symptoms, as well as resilience. From the diagrammatic formulation, a narrative formulation can be developed. The case formulation tool can be shared with the client, used to guide treatment planning, in supervision, and in case consultations. The use of the tool is explained and its clinical applications demonstrated with case examples.