New strategies are needed to improve access to cognitive and behavioral therapies for patients with persistent pain. The purpose of this randomized, controlled trial was to determine the effectiveness of the Chronic Pain Management Program, an 8-week online intervention targeting cognitive, emotional, behavioral, and social pain determinants. Program efficacy and engagement was evaluated for 92 individuals with a diagnosis of chronic noncancer pain who had a current opioid prescription. Participants were recruited from primary care practices and Internet sites, then randomly assigned to receive access to the intervention either immediately (treatment group) or after an 8-week delay (wait-list comparison). Biweekly self-report measurements were collected using online surveys on pain, depressive symptoms, pain self-management behaviors, and health care utilization during the 8-week trial. Additional measurements of opioid misuse behaviors, pain self-efficacy, and medicine regimens were completed at baseline and week 8. Engagement was evaluated by examining completion of program learning modules. The results from analysis of variance showed that at week 8, the treatment group had significantly greater improvements on pain self-efficacy and opioid misuse measures than the wait-list comparison group. Engagement level was positively associated with improvements in pain intensity, pain interference, and pain self-efficacy. In conclusion, patients on opioids were able to engage and demonstrate positive outcomes using an Internet-based self-management program. Future efforts toward heightening engagement could further maximize impacts.