Psychotherapy is best guided by theoretically driven individualized understanding of a patient’s problems; essentially a psychopathology formulation. The manifestation of Separation Anxiety Disorder (SAD) in adolescence is unique in its presentation and implications for adult mental health. This paper presents a case report of psychotherapy with an adolescent girl diagnosed with SAD. The therapeutic delivery and processes were guided by a psychopathology formulation based on the object relations school. This case report highlights the pertinence of psychopathology formulations in clinical practice; thus, demurring the dominance of diagnostically driven psychotherapeutic practice.