The aim of this single-case study was to investigate the responses to psychodynamic art psychotherapy from a man who had a diagnosis of antisocial personality disorder and ongoing aggressive behavior in a secure care setting. The intervention was 19 sessions of psychodynamic art psychotherapy lasting up to 1 hr per week. This study uses a single-case design with pretreatment, treatment, and posttreatment follow-up assessment of symptoms using multiple methods reported by the therapist, other staff members, and the patient. Treatment progress was assessed by (a) repeated self-report symptom measurements, (b) continuous assessment of observed aggressive behavior and risk incident reports in the hospital, (c) pre—post treatment assessment of relationship patterns and interpersonal schemas, and (d) interviews with the patient and his nurse at 9-month follow-up, retrospectively assessing the change. The patient showed a clinically significant reduction pre—post and pre—follow-up in symptoms. Behavioral observations indicated a reduction of overt aggression and risk-related incidents. Comparison of the Core Conflictual Relationship Theme pre—post treatment indicated positive changes in interpersonal schemas. This illustrative systematic single-case study highlights the potential for investigation of a novel psychotherapeutic approach that has in turn led to further developments in clinical research. (PsycINFO Database Record (c) 2019 APA, all rights reserved)