Aggression is a major challenge on child/adolescent inpatient psychiatric units. A screening instrument to accurately identify risk is urgently needed. To determine the predictive validity of the Brief Rating of Aggression by Children and Adolescents (BRACHA). Prospective cohort study. BRACHA is administered by clinical staff in the emergency department (ED) prior to inpatient psychiatric admission. A consecutive sample of 10,054 admitted patients from 2010-2021. No patients refused screening nor were excluded. BRACHA administered to patients in the ED prior to admission at Cincinnati Children's Hospital Medical Center (CCHMC). Patient behavioral outcomes measured by Overt Aggression Scale (OAS), categorizing aggression as verbal or physical, then as towards self, others, or objects. Female patients comprised 53.6% (n = 5,386) of the sample. Most patients were white (n = 6,556, 65.2%). Patients ranged in age from 4 to 18 years, with a mean age of 13.6 ± 3.1 years. A single biological parent (n = 5,317, 52.9%) was the predominant living arrangement among patients. The Area Under the Curve (AUC), as an assessment of predictive validity across all possible cut-offs of BRACHA scores ranged from 0.640 (aggression to self) to 0.758 (physical aggression towards others). Our findings support the BRACHA as a useful predictive instrument for aggression in inpatient psychiatric admissions from ED regardless of length of stay. Treating staff are then able to immediately classify risk level and inform care plans for all lengths of hospitalization. Applies to potential risk for aggression, except for self-aggression. Future data analyses will evaluate demographic factors to determine which improve predictive power of the BRACHA and can be used to create a BRACHA calculator. To our knowledge, this naturalistic outcomes study is one of the largest in psychiatry. The BRACHA will continue to be studied to evaluate risk for aggression on inpatient units and aim to assist in keeping unit staff and patients safe.