Students with internalizing behavior patterns are often overlooked and underserved in schools, which is problematic in that they are at risk for a host of negative outcomes. As a result, there is a need for universal screening procedures to proactively detect students with these behavior patterns and to provide them with early, ongoing supports. The purpose of this study was to examine the reliability, validity, and classification accuracy of the Student Internalizing Behavior Screener using a sample of elementary-age students. The results indicated that the screener demonstrated adequate evidence of reliability and validity. Results also revealed an optimal cutoff score to maximize accurate hits and minimize diagnostic errors, and they demonstrated that the screener was able to identify a unique group of behaviorally and emotionally at-risk students. The implications of the results are discussed, as well as the directions for future research on screening practices for students with internalizing behavior patterns.