STUDY OBJECTIVE(S): To evaluate the cost-effectiveness of implementation facilitation compared with a standard educational strategy to promote emergency department (ED)-initiated buprenorphine with linkage to ongoing opioid use disorder care in the community, from a health care-sector perspective. METHODS: A prospective cost-effectiveness analysis was conducted alongside "Project ED Health" (CTN-0069), a hybrid type 3 implementation-effectiveness study conducted at 4 academic EDs. Resources were gathered and valued according to the health care-sector perspective. Three effectiveness measures were evaluated: quality-adjusted life-years, opioid-free years, and patient engagement in community-based opioid use disorder care on the 30th day following the index ED visit. An incremental cost-effectiveness ratio was calculated for each measure of effectiveness. Likelihood of cost-effectiveness was evaluated across a wide range of "value" thresholds through cost-effectiveness acceptability curves. RESULTS: The mean, per-person, health care-sector cost associated with ED-administered buprenorphine following implementation facilitation did not differ significantly from that of standard education (,239 versus ,904), whereas the mean effectiveness for all 3 measures significantly favored the implementation facilitation strategy. Implementation facilitation has a 74% to 75% probability of being considered cost-effective from a health care-sector perspective at the recommended value range of 00,000 to 00,000 per quality-adjusted life-year. Incremental cost-effectiveness ratios estimated using secondary effectiveness measures had a 75% probability of being considered cost-effective at 5,000 per opioid-free year and 8,000 per engagement. CONCLUSION: Implementation facilitation, relative to a standard educational strategy, has a moderate-to-high likelihood of being considered cost-effective from a health care-sector perspective, depending on decisionmakers' willingness to pay for units of effectiveness.