Assessing youth psychopathology involves collecting multiple informants' reports. Yet, multi-informant reports often disagree, necessitating integrative strategies that optimize predictive power. The "Trait" score approach leverages principal components analysis (PCA) to account for the context and perspective from which informants provide reports. This approach may boost the predictive power of multi-informant reports and thus warrants rigorous testing. We tested the "Trait" score approach using multi-informant reports of adolescent social anxiety in a mixed clinical/community sample of adolescents (n=127). The "Trait" score incrementally predicted observed social anxiety ([beta]s: 0.47-0.67) and referral status (ORs: 2.66-6.53), above-and-beyond individual informants' reports and a composite of informants' reports. The "Trait" score predicted observed behavior at magnitudes well above those typically observed for individual informants' reports of internalizing psychopathology (i.e., rs=0.01-0.15). Findings demonstrate the ability of the Trait score to improve prediction of clinical indices, and potentially transform widely used practices in multi-informant assessments. [This paper was published in "Clinical Psychological Science" v8 n6 p953-970 2020.]