Introduction Child abuse and neglect are associated with increased risk of adult PTSD and dissociation. Recent research suggests that dissociation mediates the relationship between child maltreatment and PTSD, however, there is a lack of clarity regarding the mediating role of dissociation for different types of child abuse. Objective The aim of the current study was to investigate dissociation as a mediator between 5 typologies of child maltreatment and posttraumatic stress severity. Method In a sample of highly symptomatic, treatment-seeking females (n = 99), structural equation modelling was used to test 3 different models of mediation: direct effect, indirect effect, and direct and indirect effect. Results The 5 typologies of child maltreatment were significantly related to dissociation and posttraumatic stress. Dissociation mediated the effect of childhood sexual abuse and childhood emotional abuse on posttraumatic stress severity. The indirect effect model fit the data best. Conclusion Dissociation fully mediated the relationship between childhood sexual and emotional abuse and posttraumatic stress severity. The results are limited by the use of retrospective self-report measures and a small sample size.