The role of adaptive beliefs and attitudes against suicide has not been given adequate attention in the clinical or assessment literature. This article reports on the development and initial psychometric properties of a 32-item self-report inventory, the Reasons for Living Inventory for Adolescents (RFL-A). In Phase 1, we used exploratory and confirmatory factor analyses to identify five correlated factors: Future Optimism, Suicide-Related Concerns, Family Alliance, Peer Acceptance and Support, and Self-Acceptance. In Phase 2, we cross-validated the 5-factor oblique model in a different group of adolescents recruited from two high schools. In addition, we examined evidence for convergent, discriminant, and construct validities. The coefficient alpha indices for the RFL-A total and scales were satisfactory. In Phase 3, we evaluated additional evidence of reliability and validity using samples of high school and psychiatric inpatient adolescents. The results suggest that the RFL-A is a short, reliable, and valid measure that is potentially useful in the assessment of adolescent suicidal behavior.