Core symptoms of borderline personality disorder (BPD), such as emotion regulation difficulties, demonstrate considerable symptom overlap with other emotion-related disorders, namely anxiety and depression. Research suggests that heightened neuroticism and the cognitive process of repetitive negative thinking (RNT) are shared features and notable risk factors across these three disorders. However, previous research has yet to investigate the incremental validity of different forms of RNT over facet-level neuroticism traits in predicting and differentiating these forms of psychopathology. This study extends previous research by investigating the incremental validity of rumination and worry in predicting symptoms of three forms of psychopathology (i.e., BPD, depression, and anxiety) above facet-level neuroticism traits. Participants were 403 undergraduate students who completed measures assessing neuroticism, depressive rumination, anger rumination, self-critical rumination, worry, depressive symptoms, anxious symptoms, and BPD symptoms. Depressive rumination and worry predicted all three forms of psychopathology after accounting for the underlying neuroticism personality facets. Further, anger rumination was predictive of BPD symptoms and depressive symptoms. The anger and self-consciousness neuroticism facets were uniquely associated with BPD symptoms, whereas the depression and vulnerability neuroticism facets were ubiquitously associated with all three forms of psychopathology. This study highlights potential transdiagnostic cognitive processes and trait risk factors, as well as distinguishing facet-level traits and types of RNT, that could impact treatment approaches to emotion-related disorders. Future research is needed to disentangle the potential causal relationships between specific neuroticism facets, forms of repetitive negative thinking, and psychopathology development.