The present study examined whether pain catastrophizing and pain acceptance, two important targets of psychosocial interventions for chronic pain, are uniquely associated with pain severity and pain interference among patients on methadone maintenance treatment (MMT).A total of 133 MMT patients who reported experiencing some pain during the previous week completed a battery of self-report measures. Multiple regression was used to test whether pain catastrophizing and pain acceptance are related to pain severity and pain interference above and beyond covariates including demographics, emotional distress, and current methadone dose.Both pain acceptance and catastrophizing were significantly associated with pain severity and pain interference while controlling for covariates.Consistent with previous literature on patients with chronic pain but without opioid use disorder, our findings suggest that both pain catastrophizing and pain acceptance are potentially important intervention targets among MMT patients with co-occurring opioid use disorder and chronic pain.