The present study investigated the association between attachment insecurity and relational aggression among emerging adults in Guam with relational interdependence and gender as moderators of this association. The authors proposed that highly insecure individuals are more likely to be relationally aggressive, especially if they are relationally interdependent and female. One hundred ninety-nine emerging adults (67% female) were recruited from a public university in Guam. The results demonstrated anxiously attached males exhibited high levels of relational aggression when highly interdependent, whereas anxiously attached females showed high levels of proactive relational aggression when low in relational interdependence. In other words, anxiously attached individuals enact relational aggression depending on their levels of relational interdependence and gender. These results are discussed using the relational-interdependent vulnerability model and gender nonconforming theory within the culture of Guam. Significant results were not found for physical aggression. (PsycINFO Database Record (c) 2019 APA, all rights reserved)