Objective Few studies have explored the effectiveness of short-term psychodynamic psychotherapy in children and adolescents. We aimed to investigate its efficacy in a heterogeneous group of young patients. We also wanted to check any relation between the improvement and patients’ age, sex, or diagnostic category. Methods We recruited a group of 123 patients (11 to 19 years old) with a diagnosis of psychiatric disorders confirmed by Kiddie Schedule for Affective Disorders and Schizophrenia (KSADS). All participants received eight sessions of psychodynamic psychotherapy (“Brief Individuation Psychotherapy” by Senise). They were assessed using the Clinical Global Impression (Severity at baseline, Improvement after treatment), and the Children’s Global Assessment Scale (C-GAS). Results We found a clinically meaningful improvement in most patients (CGI-I 3 or lower; 79 out of 123, 64.2%) and a statistically significant improvement in the overall functioning (as measured by the C-GAS; p<0.001). We found no effect of age or sex of the patient on results obtained; patients with an externalizing disorder had significantly poorer results. Conclusion Our study, although lacking a control group, supports the possibility to use short-term psychodynamic psychotherapy in the treatment of psychiatric disorders in preadolescents and adolescents affected by psychiatric disorders.