The combination of prescription opioid dependence and chronic pain is increasingly prevalent and hazardous to public health. Variability in pain may explain poor prescription opioid addiction treatment outcomes in persons with chronic pain. This study examined pain trajectories and pain volatility in patients with chronic pain receiving treatment for prescription opioid addiction. We conducted secondary analyses of adults with chronic pain (n = 149) who received buprenorphine/naloxone (BUP/NLX) and counseling for 12 weeks in an outpatient, multisite clinical trial. Good treatment outcome was defined as urine-verified abstinence from opioids at treatment endpoint (Week 12) and during at least 2 of the previous 3 weeks. Pain severity significantly declined over time during treatment (b = −0.36, p < .001). Patients with greater pain volatility were less likely to have a good treatment outcome (odds ratio = 0.55, p < .05), controlling for baseline pain severity and rate of change in pain over time. A 1 standard deviation increase in pain volatility was associated with a 44% reduction in the probability of endpoint abstinence. The significant reduction in subjective pain during treatment provides observational support for the analgesic effects of BUP/NLX in patients with chronic pain and opioid dependence. Patients with greater volatility in subjective pain during treatment have increased risk of returning to opioid use by the conclusion of an intensive treatment with BUP/NLX and counseling. Future research should examine underlying mechanisms of pain volatility and identify related therapeutic targets to optimize interventions for prescription opioid addiction and co-occurring chronic pain.