The theory that borderline personality disorder (BPD) is associated with experiential avoidance, and that experiential avoidance mediates the association between BPD and deliberate, nonsuicidal self-harm was examined. Female inmate participants (N = 105) were given structured diagnostic assessments of BPD, as well as several measures of experiential avoidance. There was a high lifetime prevalence of past self-harm (47.6%). Higher dimensional scores representing BPD severity were associated with higher self-harm frequency and greater experiential avoidance. Structural equation modeling analyses indicated that experiential avoidance did not mediate the association between BPD and self-harm, although thought suppression was associated with self-harm frequency.