Despite theoretical links between attachment quality in early childhood and subsequent internalizing symptoms, there is limited empirical evidence supporting direct effects. In this article, we test whether early attachment insecurity indirectly contributes to adolescent internalizing by increasing the likelihood of certain pathways leading to elevated symptoms (i.e., moderated mediation). Structural equation modeling and bootstrapping were used to test for moderated mediation using longitudinal data from 910 adolescents participating in the National Institute of Child Health and Human Development Study of Early Child Care ("M" age = 15.1; 50% female, 23% racial/ethnic minority). Among dyads with a history of an insecure attachment in early childhood, mothers' negative emotions during the transition to adolescence significantly predicted less availability during parent-adolescent interactions, which in turn increased adolescents' preoccupation with parental relationships. The same process was not evident in youth with a history of secure attachments. However, the extent to which preoccupation with parental relationships was associated with increases in internalizing symptoms depended on both attachment history and gender. Results highlight one pathway by which early attachment history may indirectly contribute to increased internalizing symptoms for girls during the transition to adolescence. (Contains 4 figures and 4 tables.)