Background: Secure attachment in adulthood is associated with many markers of adaptive functioning. Valid and reliable self-report measures of attachment security could provide a practical tool to help advance strengths-based research and clinical work. Previous reviews have not specifically examined the psychometric properties of self-report instruments with respect to secure attachment or systematically appraised the methodological quality of relevant validation studies.Method: A systematic review was completed in accordance with the COSMIN guidelines for reviews of patient-reported outcome measures. The methodological quality of individual studies was evaluated, and results were rated against criteria for good measurement properties.Results: A total of 40 studies were included in the review, which collectively reported on 24 self-report instruments. The methodological quality of individual studies was variable, and no single instrument was identified as having sufficient evidence of a range of psychometric properties. However, the Attachment Style Questionnaire-Short Form (ASQ-SF), the Cartes-Modèles Individuels de Relations (CAMIR), Cartes-Modèles Individuels de Relations-Reduced (CAMIR-R), and the Psychological Treatment Inventory-Attachment Style Scales (PTI-ASS) had the most robust evidence for the properties assessed. Conclusion:Existing self-report measures assessing adult secure attachment have limited psychometric support. More methodologically robust studies of content validity, reliability, measurement invariance, and construct validity in particular are needed.