Strengths constitute an important element of developmental assessments. It is consistent with evidence-based practice to use assessment tools that adequately measure a given construct and are appropriate for use with their targeted population. The Strengths Assessment Inventory–Youth Version (SAI-Y; Rawana & Brownlee, 2010)—a self-report measure of personal strengths, self-concept, and emotional functioning—was administered to 230 male and female adolescent offenders. Confirmatory factor analyses revealed that the SAI-Y’s factor structure demonstrated an acceptable fit overall, while some factors fit the data well, and fewer factors displayed a questionable fit. A majority of scale scores were found to exhibit good reliability for both sexes, with three empirical scale scores demonstrating poor reliability. In addition, scores on the SAI-Y also achieved satisfactory convergent and divergent validity. Total strength scores were significantly correlated in the expected direction with most theoretically related measures of emotional and behavioral functioning (e.g., self-esteem, treatment readiness, antisocial attitudes). Lastly, moderate gender effects and small ethnicity differences in response patterns were found. This was the first validation study of the SAI-Y with a justice-involved sample and the results suggest it is an appropriate measure for use with both male and female justice-involved young persons in detention and in the community.