Chronic pain and posttraumatic stress disorder (PTSD) are highly comorbid conditions, often associated with a significant level of affective distress and physical disability. Patients with chronic pain have higher rates of PTSD. Likewise, patients with PTSD are often diagnosed with numerous chronic pain conditions. Despite the high comorbidity, it is still unknown why pain and PTSD symptoms coexist. Throughout the past few decades, the literature relating to chronic pain and PTSD has become progressively more sophisticated, resulting in well-supported theories and treatments for sufferers. However, only a handful of studies have specifically addressed the co-occurrence of these two disorders. Different physiological, psychological and behavioral mechanisms could explain the association between them. Clinical practice and research suggest that chronic pain and PTSD are mutually maintaining conditions, interacting in such a way as to negatively impact the course of either disorder, treatment outcomes and patient’s quality of life. There are several pathways by which both disorders may be involved in the escalation of symptoms and distress following trauma. Therefore, it is important in clinical settings to understand the impact of PTSD on chronic pain and vice versa. In the evaluation and treatment of patients with chronic pain and PTSD comorbidity multidisciplinary approach is required, which leads to better outcomes and reduces the cost of treatment.