Background: Growing evidence shows the significance of illness and surgical procedures as traumatizing stressors. Risk factors are widely investigated in various settings and samples, using numerous measures of posttraumatic stress and posttraumatic stress disorder (PTSD). While pretrauma psychological distress is acknowledged as an influential factor, peritraumatic experiences are controversially still being discussed as relevant to the development of PTSD. Objective: In a group of patients consecutively undergoing elective spine surgery (N = 89) in a German hospital, this longitudinal study addressed the question of how pretrauma PTSD symptoms and peritrauma distress interact with one another in regard to the amount of posttrauma symptoms of PTSD. Methods: Pre- and posttrauma symptoms of PTSD as well as peritrauma distress were assessed through questionnaires one week before, one week after or three months after surgery. Results: Even though all three variables showed significant correlations with one another, mediation analysis revealed that peritrauma distress fully mediated the relationship between pre- and posttrauma PTSD symptoms. Conclusions: These results add new insights to the controversial discussion on the role peritraumatic experiences play in the development of PTSD, especially in medical settings.