The co-occurrence of posttraumatic stress disorder (PTSD) pathology with a substance use disorder (SUD) is associated with emotion regulation deficits. However, studies in this area generally rely on trait-based emotion regulation measures, and there is limited information on the relation of PTSD pathology to the use of specific emotion regulation strategies in response to trauma-related distress among SUD patients or the consequences of these strategies for trauma cue reactivity. This study examined the relation of PTSD symptom severity to the use of specific emotion regulation strategies during trauma cue exposure among trauma-exposed SUD patients, as well as the indirect relations of PTSD symptom severity to changes in negative affect, cravings, and cortisol levels pre- to posttrauma cue exposure through different emotion regulation strategies. Participants were 133 trauma-exposed SUD patients. Participants listened to a personalized trauma script and reported on emotion regulation strategies used during the script. Data on negative affect, cravings, and cortisol were collected pre- and postscript. PTSD symptom severity related positively to the use of more adaptive (e.g., distraction) and maladaptive (e.g., suppression) regulation strategies. Moreover, evidence for the indirect effects of PTSD symptom severity on negative affect and cortisol reactivity through both adaptive and maladaptive emotion regulation strategies was found. Implications of findings are discussed.