Although borderline personality disorder (BPD) features consistently show strong relations with chronic pain, the mechanisms underlying this association remain unclear. BPD is characterized by dysregulated emotion. Given previously observed relationships between emotion dysregulation and pain, we hypothesized that components of this dysregulation—elevated and labile negative affect and emotion sensitivity—would account for the relationship between BPD features and various pain complaints in a chronic pain patient sample. Specifically, we hypothesized that negative affect would indirectly predict pain through higher emotion sensitivity to pain, operationalized as pain anxiety sensitivity. To test these hypotheses, we administered a series of self-report measures to 147 patients at a chronic pain treatment facility. As expected, BPD features predicted pain severity (β = .19, p = .029), activity interference from pain (β = .22, p = .015), and affective interference from pain (β = .41, p < .001). Using path analyses, we found that the associations between BPD features and pain severity and interference were accounted for by serial indirect pathways through affective lability then pain anxiety and, to a lesser extent, through trait anxiety then pain anxiety. This is the first study to demonstrate roles for affective lability and pain anxiety sensitivity in the association between BPD features and chronic pain complaints in a chronic pain sample. We discuss implications for the relationship between dysregulated emotion and pain as well as for psychologically-focused treatment interventions for pain.