This study examines the association between buprenorphine treatment in the emergency department (ED) and follow-up engagement in opioid use disorder (OUD) treatment 1 month later. The study involved 464 ED patients with OUD, most of whom were men, non-Hispanic White, and had Medicaid insurance. Over 50% had unstable housing, and most had comorbid mental health conditions. High interest in buprenorphine treatment was observed, with 85.8% receiving treatment, and 58.0% receiving it in the ED. Among those who received ED buprenorphine treatment, 49.7% remained engaged in OUD treatment at 30 days, compared to 22.7% who did not receive ED treatment. The study found that ED buprenorphine treatment was associated with a 2-fold higher likelihood of 30-day OUD treatment engagement (adjusted risk ratio, 1.97; 95% CI, 1.27-3.07). These findings suggest that ED buprenorphine treatment is an effective strategy to support follow-up care for patients with OUD. The study highlights the importance of improving access to buprenorphine in EDs to address the opioid crisis. Future research should focus on optimizing both the uptake and effectiveness of buprenorphine initiation in low-threshold settings like the ED. The study was conducted in California, and the findings may not be generalizable to other regions. Limitations include potential selection bias and incomplete data. The study underscores the critical role of EDs in OUD treatment and the need for additional interventions to reach patients who do not receive ED buprenorphine treatment.This study examines the association between buprenorphine treatment in the emergency department (ED) and follow-up engagement in opioid use disorder (OUD) treatment 1 month later. The study involved 464 ED patients with OUD, most of whom were men, non-Hispanic White, and had Medicaid insurance. Over 50% had unstable housing, and most had comorbid mental health conditions. High interest in buprenorphine treatment was observed, with 85.8% receiving treatment, and 58.0% receiving it in the ED. Among those who received ED buprenorphine treatment, 49.7% remained engaged in OUD treatment at 30 days, compared to 22.7% who did not receive ED treatment. The study found that ED buprenorphine treatment was associated with a 2-fold higher likelihood of 30-day OUD treatment engagement (adjusted risk ratio, 1.97; 95% CI, 1.27-3.07). These findings suggest that ED buprenorphine treatment is an effective strategy to support follow-up care for patients with OUD. The study highlights the importance of improving access to buprenorphine in EDs to address the opioid crisis. Future research should focus on optimizing both the uptake and effectiveness of buprenorphine initiation in low-threshold settings like the ED. The study was conducted in California, and the findings may not be generalizable to other regions. Limitations include potential selection bias and incomplete data. The study underscores the critical role of EDs in OUD treatment and the need for additional interventions to reach patients who do not receive ED buprenorphine treatment.