Over the past decade, considerable research has accumulated showing that chronic pain patients experiencing high levels of negative affect (i.e., anxiety, depression) are at increased risk for prescription opioid misuse. The primary objective of the present study was to examine the factors that underlie the association between negative affect (NA) and prescription opioid misuse among patients with chronic pain. In this study, 82 patients with chronic musculoskeletal pain being prescribed opioid medication completed the Current Opioid Misuse Measure (COMM), a well-validated self-report questionnaire designed to assess prescription opioid misuse. Patients were also asked to complete self-report measures of pain intensity, NA, and opioid craving. A bootstrapped multiple mediation analysis was used to examine the mediating role of patients’ pain intensity and opioid craving in the association between NA and prescription opioid misuse. Consistent with previous research, we found a significant association between NA and prescription opioid misuse. Interestingly, results revealed that opioid craving, but not pain intensity, mediated the association between NA and opioid misuse. Discussion addresses the potential psychological and neurobiological factors that might contribute to the inter-relationships between NA, opioid craving, and prescription opioid misuse in patients with pain. The clinical implications of our findings are also discussed.