BACKGROUND: Methadone maintenance therapy (MMT) is an efficacious form of medication assisted treatment for opioid use disorder (OUD), yet many individuals on MMT relapse. Chronic pain and deficits in positive affective response to natural rewards may result in dysphoria that fuels opioid craving and promotes relapse. As such, behavioral therapies that ameliorate chronic pain and enhance positive affect may serve as useful adjuncts to MMT. This analysis of ecological momentary assessment (EMA) data from a Stage 1 randomized clinical trial examined effects of Mindfulness-Oriented Recovery Enhancement (MORE) on opioid craving, pain, and positive affective state. METHODS: Participants with OUD and chronic pain (N = 30) were randomized to 8 weeks of MORE or treatment as usual (TAU). Across 8 weeks of treatment, participants completed up to 112 random EMA measures of craving, pain, and affect, as well as event-contingent craving ratings. Multilevel models examined the effects of MORE on craving, pain, and affect, as well as the association between positive affect and craving. RESULTS: EMA showed significantly greater improvements in craving, pain unpleasantness, stress, and positive affect for participants in MORE than for participants in TAU. Participants in MORE reported having nearly 1.3 times greater self-control over craving than those in TAU. Further, positive affect was associated with reduced craving, an association that was significantly stronger among participants in MORE than TAU. CONCLUSION: MORE may be a useful non-pharmacological adjunct among individuals with OUD and chronic pain in MMT.