Previous studies have demonstrated a link between PTSD and smartphone addiction; however, few studies have examined what may account for this relationship. The current study sought to examine whether problem-focused, emotion-focused, and avoidance-focused coping impacts this relationship among young adults. The study consisted of 538 young adults with potential trauma exposure who completed an online survey assessing PTSD symptoms, coping strategies, and problematic smartphone use. PTSD was associated with problematic smartphone use and all styles of coping, while problematic smartphone use was associated with avoidance coping and emotion-focused coping. Analyses of indirect effects demonstrated that PTSD was indirectly associated with problematic smartphone use via avoidance coping but not problem-focused or emotion-focused coping. Findings indicate that avoidance may play an important role in promoting problematic smartphone use among individuals with trauma-related distress and suggest that approaches aimed at targeting avoidance may be beneficial to both PTSD symptoms and problematic smartphone use.