Background Despite empirical evidence suggesting complex associations between childhood trauma and self‐harm, there is a dearth of research investigating this association in the female prison population. The current study explored pathways to self‐harm following childhood trauma, by investigating the mediating roles of Post‐traumatic Stress Disorder (PTSD) symptoms, emotion regulation and dissociation, in this relationship, within a sample of 89 female prisoners. Methods Cross‐sectional, interview‐format, questionnaire study within a female prison population. Measures of childhood trauma, self‐harm, PTSD, emotion regulation and dissociation were administered. Results The majority of the sample (58.4%) reported history of self‐harm. Bootstrapped mediation analyses indicated an indirect effect of emotion regulation on the relationship between childhood trauma and self‐harm. An indirect effect was also found for PTSD arousal/reactivity cluster of symptoms. Multiple mediation analyses revealed that interactional effects were present for emotion regulation and arousal/reactivity, and emotion regulation and dissociation, respectively. Conclusion Self‐harm is highly prevalent among female prisoners. Interventions promoting emotion regulation and addressing arousal/reactivity symptoms following traumatization may provide an effective way of addressing this problem. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Messages Self‐harm is highly prevalent amongst female prisoners, occurring in 58.4% of this sample. Emotion regulation and the arousal/reactivity symptom cluster of PTSD were found to mediate the relationship between childhood trauma and self‐harm, both independently and simultaneously. Emotion regulation and dissociation were found to interactionally mediate this relationship. Strategies targeting emotion dysregulation and hyperarousal symptoms, amongst female prisoners who have experienced childhood trauma, may be helpful in reducing self‐harming behaviours.