Childhood abuse (CA) is a risk factor for trauma-related disorders including posttraumatic stress disorder (PTSD) and complex posttraumatic stress disorder (CPTSD). This severe form of interpersonal trauma may result in “identification with the aggressor” (IWA), in which the individual may take on the beliefs, perspectives, and behaviors of the perpetrator. Although previous evidence suggests that IWA may be particularly related to CPTSD as compared to PTSD, there has been no study that investigated this hypothesis. Objective The current study explored the relations between IWA and PTSD and CPTSD symptoms, and the contribution of IWA to the excess probability of PTSD and CPTSD classifications, as compared to no classification. Participants and setting This cross-sectional study was conducted among 320 Israeli adult CA survivors aged 21–63 (M = 42.04, SD = 10.81). Methods An online survey was completed by a convenience sample of adult CA survivors. Results Replacing one's agency with that of the perpetrator as part of IWA had a significant effect on both PTSD and CPTSD symptoms (ES = 0.36 and 0.24, respectively), and served as a risk factor for both PTSD and CPTSD classifications. Moreover, analysis of the models' predicted values reveals that the predicted probability of CPTSD classification was 3 to 5 times higher than on the probability of PTSD classifications, for low to high values of the replacing one's agency scale, respectively. Conclusions The current findings suggest that IWA may describe some of the deep and long-lasting detriments of CA on self, and may contribute to the development of CPTSD symptoms.