Background: Post-traumatic stress disorder often brings about profound, lasting, structural changes to one's sense of self. Aims: This study investigated self-complexity and self-aspect control in post-traumatic stress disorder (PTSD). Method: Trauma survivors with (n = 103) and without (n = 102) PTSD completed an online questionnaire which involved the completion of a self-complexity task and measures of PTSD. Results: It was found that those with PTSD had significantly greater overall self-complexity than those without PTSD. Furthermore, when considering self-description valence, it was found that those with PTSD had significantly greater negative self-complexity than those without PTSD, but the groups did not differ in terms of positive self-complexity. Second, those with PTSD reported significantly less control over their self-aspects. Third, for those with PTSD, lower levels of self-aspect control were significantly correlated with greater negative self-complexity and lower positive self-complexity. Finally, self-aspect control mediated the relationship between self-complexity and PTSD symptoms. Conclusion: The theoretical implications for PTSD models and the clinical implications for the treatment of those with PTSD are explored.