Background: There is evidence that incarcerated people show higher rates of symptoms of psychopathology. In the present study, we assessed male Iranian incarcerated people with borderline personality disorders (BPD) and investigated the occurrence of past and current trauma and their associations with dissociative experiences. Methods: A total of 69 male Iranian incarcerated people (mean age: 33.76 years) diagnosed with PBD completed questionnaires covering sociodemographic information, dissociative experiences, and past and current traumatic events. Results: Participants reporting the occurrence of childhood trauma also reported the occurrence of adulthood trauma. Dissociation and adulthood trauma were associated in a U-shaped, non-linear fashion: Low and high adulthood trauma were associated with higher dissociation. Younger age, the presence of childhood trauma, and being single or divorced predicted adulthood trauma. Conclusion: The pattern of results suggests that both childhood and adulthood trauma are highly prevalent among male incarcerated people, while the association between adulthood trauma and dissociation appeared to be more complex. When treating male incarcerated people, a complex interplay between past and current traumas and dissociation should be considered.