The Psychodynamic Diagnostic Manual—Second Edition (PDM-2) stresses the importance of the integration between a descriptive and functional understanding of clinical phenomena in order to enhance a person-based nosology. The present article aims to discuss a clinical case of a patient suffering from generalized anxiety disorder, currently considered a controversial diagnosis, in order to illustrate some of the complexities and advantages of the PDM-2 model in the psychodiagnostic description, case formulation, and treatment planning. To do so, we applied the Psychodiagnostic Chart—Second Edition (PDC-2) to an Adult Attachment Interview (AAI) transcript, and, to the best of our knowledge, this is the first study that pursued this goal. As a clinical-research method, the AAI represents a useful tool in order to explore patients’ mental states and internalized object relations, crucial aspects in personality organization. Furthermore, the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) Axis I Disorders and Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II) were used in order to code the S-Axis. Symptoms were discussed in light of the other PDC-2 sections. Results demonstrated how the PDC-2 can add further crucial information to what symptoms-based assessment tools already provide. Despite there being no SCID-II personality disorders recorded, finer-grained analysis from the PDC-2 method showed an underlying borderline personality organization with highly relevant consequences on treatment planning. Indeed, this fundamental tool allows us to reflect on a wider range of patient’s issues that need to be addressed in treatment. For this reason, we stress the importance of PDC-2 as a useful instrument in clinical assessment that could also provide a helpful dialogue frame for scholars with different theoretical backgrounds.