Depersonalization/derealization disorder is a dissociative disorder characterized by persistent unreality experiences and intact reality testing. It is presented as a primary disorder or conceptualized as a secondary disorder associated with another psychopathology, in which such secondary disorder supposes to be the main promoting factor in the condition. Dissociative disorders are understood broadly as posttraumatic phenomena, although literature reports have demonstrated certain difficulties in both treatment and accurate diagnosis especially concerning depersonalization/derealization. The present theoretical paper aims to present previous research data and a summarized theoretical corpus on trauma-related dissociation to characterize the phenomenon from a psychotraumatology standpoint, and elaborate an explanatory hypothesis on its mechanism, pointing to etiology, differential diagnosis, and adequate management issues based on historical and empirical research to date. As an attainable emotional reaction, the chronic egodystonic presentation requires a formal explanation in conformity with the theory of structural dissociation. Depersonalization/derealization disorder, as a dissociative disorder, although mostly would be precipitated by accumulative trauma, could be understood not always solely on that explanation, but as a multifactorial phenomenon in some cases. Nonetheless, an explanation centered in the disorder acquisition as a type of posttraumatic reaction will be emphasized, involving personality development and developmental psychopathology.