Attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) are common childhood syndromes that exhibit a high degree of comorbidity. Both ADHD and ODD symptoms in childhood predict higher levels of borderline personality features (BPF) later in development. Yet ADHD, ODD, and BPF each consist of a heterogeneous group of symptoms, and symptom-level associations between these groups remain unclear. The present study examined symptom-level associations, as well as sex differences in symptom-level associations, among ADHD, ODD, and BPF using network analysis. Caregivers of 962 children between the ages of 5 and 12 completed rating scales of ADHD, ODD, and BPF. Assessment of Bridge Expected Influence indicated a number of bridge symptoms linking ADHD to ODD; these bridge symptoms were primarily from the hyperactive-impulsive (rather than the inattentive) dimension of ADHD (e.g., blurts out answers, leaves seat, runs excessively). A smaller number of bridge symptoms were identified linking ADHD and ODD to BPF, and these bridge symptoms were different for girls versus boys. Overall, several ADHD hyperactive-impulsive symptoms were related to the BPF item gets in trouble for doing things without thinking, and the ODD item touchy/easily annoyed was related to the BPF item goes back and forth between different feelings. Moreover, whereas we observed stronger links between ODD antagonistic symptoms (e.g., blames others) and BPF among girls, we observed stronger links between ODD oppositional symptoms (e.g., defies/refuses to comply) and BPF among boys. Taken together, results provide a more nuanced, symptom-level understanding of the overlap among ADHD, ODD, and BPF.