Early maladaptive traits are predictive of later borderline personality pathology (BPP), but little is known about their dynamic interplay over time. This is an important issue to address, however, as significant differences in the ‘clinical weight’ of various traits constituting the early BPP trait phenotype may inform the field on important target constructs from an early intervention perspective. Therefore, the current study aims to uncover the complex dependencies between BPP traits across the crucial developmental period of childhood and adolescence, by using longitudinal network analysis. Both between- and within-person networks were constructed to identify how early mother-reported borderline-related traits are connected across a timespan of six years (ntime 1 = 718, Mtime1 = 10.73 years, SDtime1 = 1.39, 55.1% girls). Overall, the temporal network suggested various trait interdependencies, with internalizing traits being particularly influential in the development of the BPP trait network structure. At the same time, externalizing traits likely inhibit the negative effects of these core traits. In addition, results also revealed that internalizing and externalizing clusters of early borderline-related traits are linked through emotional lability. Implications of these findings are discussed in view of the change mechanisms at play and potential targets for early intervention.