BACKGROUND Rates of dual antiplatelet therapy (DAPT) after high-risk transient ischemic attack or minor ischemic stroke (TIAMIS) are suboptimal. We performed a cost-effectiveness analysis to characterize the parameters of a quality improvement (QI) intervention designed to increase DAPT use after TIAMIS. RESULTS We constructed a decision tree model that compared current national rates of DAPT use after TIAMIS with rates after implementing a theoretical QI intervention designed to increase appropriate DAPT use. The base case assumed that a QI intervention increased the rate of DAPT use to 65% from 45%. Costs (payer and societal) and outcomes (stroke, myocardial infarction, major bleed, or death) were modeled using a lifetime horizon. An incremental cost-effectiveness ratio <$100 000 per quality-adjusted life year was considered cost-effective. Deterministic and probabilistic sensitivity analyses were performed. From the payer perspective, a QI intervention was associated with $9657 in lifetime cost savings and 0.18 more quality-adjusted life years compared with current national treatment rates. A QI intervention was cost-effective in 73% of probabilistic sensitivity analysis iterations. Results were similar from the societal perspective. The maximum acceptable, initial, 1-time payer cost of a QI intervention was $28 032 per patient. A QI intervention that increased DAPT use to at least 51% was cost-effective in the base case. CONCLUSIONS Increasing DAPT use after TIAMIS with a QI intervention is cost-effective over a wide range of costs and proportion of patients with TIAMIS treated with DAPT after implementation of a QI intervention. Our results support the development of future interventions focused on increasing DAPT use after TIAMIS.