This case study examines therapeutic mechanisms in the work with the parents of a latency aged child, with child separation anxiety disorder, according to the DSM-5 classification. In this single–case study design, the mechanisms identified are practitioner-researcher’s intervention narratives within a theoretically informed framework that is shaped by the psychodynamic understanding of the causes and treatment for the child separation anxiety disorder. The study evaluates the process and the effectiveness of the practitioner-researcher’s treatment throughout the analysis of 11 sessions with the parents. These intervention narratives modified the often unconscious “aggressive” parental beliefs and attitudes toward the child. They also contributed to the progressive reduction and, finally, extinction of his separation anxiety disorder. The study finally demonstrates that, apart from the intervention on the current relationship dynamics between the parents and the child, parent work involves intervention in the emotional difficulties of the parents as well as intervention focused on the couple relationship problems, especially those that reinforce the separation anxiety of the child. The parents were treated in a Child and Adolescent Community Mental Health Centre in a major urban area in southern Europe, and they consented to the publication of anonymous information of the case.