Aim: The aim of this review was to evaluate the psychometric properties of outcome measures used to quantify upper limb function in children and adolescents with brachial plexus birth palsy (BPBP). Method: Eleven electronic databases were searched to identify studies on the effects of conservative management to improve upper limb function in young people with BPBP. Outcome measures used in these studies were extracted and used in a subsequent search to identify studies that evaluated the psychometric properties of these measures. The methodological quality of these studies was rated using a standardized critical appraisal tool. Results: Thirty-three outcome measures and 12 psychometric studies were identified. Nine outcome measures had some psychometric evidence, which was variable in quality. The outcome measures which seem to have the most robust psychometric properties include the Active Movement Scale, Assisting Hand Assessment, Pediatric Evaluation of Disability Index, and the Pediatric Outcomes Data Collection Instrument. Interpretation: Further research is required to determine the psychometric properties of outcome measures used for children and adolescents with BPBP. Caution is required when interpreting the results of commonly used outcome measures in this population owing to their relatively unknown psychometric properties.