The link between alliance and treatment outcome is robust. Nevertheless, few, if any, self‐report measures exist to assess the alliance between hospitalized adolescents and their treatment team as a whole. The present study looks to extend the use of a brief self‐report measure of inpatient treatment alliance designed for adult inpatients to be used with adolescents. The scale is designed incorporating items that tap the three factors of alliance (bond, goals and collaboration) to assess the alliance that the patient has with his or her treatment team. Our results show that the Inpatient‐Treatment Alliance Scale is unifactoral, shows good psychometrics and is linked in theoretically meaningful ways to global clinician ratings of engagement in individual psychotherapy. Copyright © 2014 John Wiley & Sons, Ltd. Key Practitioner Message Inpatient treatment of adolescents requires the assessment of alliance to be between the patient and his or her treatment team rather than an individual clinician. Assessment of the alliance can benefit clinicians treating hospitalized adolescents especially because these patients are difficult to engage with in treatment. This study shows that the Inpatient‐Treatment Alliance Scale is a promising measure for assessing treatment alliance on an adolescent inpatient setting.