Aim: to describe and understand an interrupted psychotherapy of a patient with Borderline Personality Disorder. Method: systematic, naturalistic and exploratory case study of the therapeutic dyad. The Therapeutic Cycles Model (TCM) and the Psychotherapy Process Q-Set (PQS) were the instruments used. Results: according to TCM, the case can be divided into two stages: one with cycles of change and one without cycles of change. According to the PQS, the themes addressed by the dyad were relevant to psychotherapy and related to patient diagnosis. However, the patient seemed to be uncommitted to the therapeutic process and did not rely on the therapist to solve her problems. The therapist's attitudes were adequate but technical interventions were not prominent. The combination of patient and therapist data assisted in understanding why the psychotherapy was abandoned. Keywords: therapeutic process; dropout of treatment; therapeutic process and outcome; psychodynamic psychotherapy; process of change Resumen: Objetivo: describir y comprender una psicoterapia interrumpida con paciente con Trastorno de Personalidad Borderline. Método: estudio de caso sistemático, naturalístico y exploratorio de dupla paciente-terapeuta. Fue utilizada la conjugación de los instrumentos Therapeutic Cycles Model (TCM) y Psychotherapy Process Q-Set (PQS). Resultados: según el TCM, el caso puede ser dividido en dos etapas: una con ciclos de cambio y una sin ciclos de cambio. Según el PQS, los contenidos abordados por la dupla eran pertinentes para la psicoterapia y relacionados al diagnóstico del paciente. Sin embargo, la paciente se revelaba descomprometida con el proceso y pasó a no contar con la terapeuta para resolver sus problemas. Las actitudes de la terapeuta eran adecuadas, pero no fueron evidenciadas técnicas características.