ABSTRACT
Despite the centrality of attachment theory in understanding close relationships, transgender and gender-diverse individuals have been largely underrepresented in attachment research. This underrepresentation raises questions about the applicability of established measurement tools to gender-diverse populations, particularly during emerging adulthood, a period marked by the reorganization of attachment bonds. The Experiences in Close Relationships scale is one of the most widely used to assess adult attachment; however, evaluating if this measure is equivalent across groups, particularly for gender-diverse individuals, is crucial for ensuring valid conclusions. This study aimed to examine the measurement invariance of the Spanish Brief Experiences in Close Relationship Scale across cisgender and gender-diverse groups. A sample of 633 emerging adults aged 18–29 years (M = 22.60, SD = 2.89) was analyzed, with 38.40% identifying as gender-diverse individuals. Factorial partial invariance analysis supported the equivalence of the SB-ECR across gender identity groups. In addition, small but statistically significant differences emerged in latent means, with TGD emerging adults reporting higher levels of attachment insecurity compared to cisgender participants. These findings highlight the importance of evaluating attachment measures in minority groups to ensure their validity and underscore the need to explore diverse attachment experiences.