Background: This study aimed to evaluate processes from the mutual maintenance model in relation to daily functioning in patients with both chronic pain and a history of a traumatic experience. The mechanism illustrated the structural relations for daily functioning among pain intensity, hyperarousal, re-experiencing, trauma avoidance, and pain avoidance. Methods: Archival data (N = 214) was used for this study and data were analyzed for 142 chronic pain patients reporting a traumatic experience and seeking treatment at a tertiary pain clinic in Korea. Results: The results indicated that pain intensity, hyperarousal, and pain avoidance had significant direct effects on daily functioning. Also, pain intensity showed significant indirect effects on daily functioning through hyperarousal and pain avoidance; and hyperarousal through pain avoidance. Conclusions: Results suggest a direct contribution of high levels of pain, hyperarousal symptoms of PTSD, and pain avoidance behaviors to reduced daily functioning. Also, elevated pain as reminders of the trauma may trigger high levels of hyperarousal symptoms of PTSD. Subsequently, avoidant coping strategies may be used to minimize pain so that the trauma would not be re-experienced, thus inhibiting the activation of hyperarousal symptoms of PTSD. However, prolonged use of such strategies may contribute to decline in daily functioning.