Background: The relationship between trauma-related negative cognitions and post-traumatic stress disorder (PTSD) symptoms has been studied frequently. Several studies found a mediating effect of trauma-related negative cognitions on symptom reduction in studies on different psychotherapeutic treatments, however, this relationship has never been studied in imagery rescripting (ImRs) or eye movement desensitization and reprocessing (EMDR).Objective: To analyse the role of trauma-related negative cognitions in the treatment of PTSD due to childhood trauma with EMDR and ImRs.Method:N = 155 patients with PTSD due to childhood trauma aged between 18 and 65 (M = 38.54) participated in a randomized clinical trial and were treated with either EMDR or ImRs in Australia, Germany, and the Netherlands between October 2014 and June 2019. We analysed the relationship between PTSD symptoms (Clinician-administered PTSD Scale for DSM-5, CAPS-5 and Impact of Event Scale revised; IES-R, completed twice for index trauma and for all other traumas) and trauma-related negative cognitions (Post-Traumatic Cognitions Inventory, PTCI) using Granger Causality analyses with linear mixed models on person-centered variables. Assessments were conducted pre-treatment, post-treatment (12 sessions in 6 weeks), eight weeks post-treatment, and one year after the pre-treatment assessment.Results: Changes in negative cognitions (PTCI) preceded changes in PTSD symptoms (unidirectional) as measured by the CAPS and the IES-R for index trauma. For the IES-R related to all other traumas, a unidirectional relationship was found in which changes in PTSD symptoms preceded changes in negative cognitions. No moderating effect of treatment was found. On the level of PTCI subscales only changes in cognitions about oneself preceeded changes in PTSD symptoms.Conclusions: The results support the idea of a general role of trauma-related negative cognitions in the treatment of PTSD. The analyses should be replicated with a higher frequency of assessments.