BACKGROUND AND HYPOTHESIS: Improvements in screening tools for early subthreshold psychosis symptoms are needed to facilitate early identification and intervention efforts, especially given the challenges of rapidly differentiating age-appropriate experiences from potential early signs of emerging psychosis. Tools can be lengthy and time-consuming, impacting their utility and accessibility across clinical settings, and age-normed data are limited. To address this gap, we sought to develop and validate a brief, empirically derived, age-normed, subthreshold psychosis screening tool, for public use. STUDY DESIGN: Computerized adaptive test simulation was used to derive a 5-item short form with age norm equivalencies from a 12-item PRIME-Screen-Revised (PRIME-12) administered to 7053 youth (Mage = 15.8, SD = 2.7; 54% female; 33% Black). Concurrent validity was assessed (n = 758) using contemporaneous administration of the PRIME-5 and the Structured Interview for Prodromal Syndromes. Comparability of criterion-related validity of the PRIME-5, PRIME-12, and Scale of Prodromal Symptoms (SOPS) was assessed by relating scores to psychosis-risk-relevant criteria. Finally, self-report versus assessor-administered PRIME total scores were compared (n = 131) to assess their concurrent validity. STUDY RESULTS: Correlations among PRIME-5, PRIME-12, and SOPS were comparable and moderate, supporting their convergent validity. The PRIME-5 also showed comparable criterion-related validity, demonstrating similar relationships with psychosis-risk indicators as the other tools. Self-reported and assessor-administered PRIME-5 were moderately correlated. CONCLUSIONS: Public availability of a brief, age-normed, and validated screening tool-which can be assessor or self-administered-will expedite and improve early identification of youth (age 11 and older) at risk for psychosis.