The study examined pain management and treatment outcomes in Medicare patients with opioid use disorder (OUD) and comorbid chronic pain who started methadone or buprenorphine. Data from 2020–2023 were analyzed for 49,727 patients (mean age 59.0 years, 49.3% female), of whom 32.5% started methadone in opioid treatment programs and 67.5% started buprenorphine in an outpatient setting. Methadone initiation was associated with lower rates of hospitalizations for pain (IRR 0.64; 95% CI [0.58–0.70]; aRD -7.2 per 1000 person-years) and fewer emergency room visits for pain (IRR 0.82; 95% CI [0.82–0.92]; aRD -10.2 per 1000 person-years) compared with buprenorphine. There was no difference in opioid overdose or all-cause mortality. Outcomes were assessed 1 year after initiation of treatment using target study emulation. Major limitations included unmeasured confounding factors and limited generalizability.