Abstract Background/Introduction Because of the poor prognosis associated with acute coronary syndromes (ACS), intensive low-density lipoprotein cholesterol (LDL-C) management therapy is recommended as early as possible after the onset of ACS, with the goal of lowering plasma LDL-C to <70 mg/dL. In Nagasaki City, a council was formed comprising all hospitals performing percutaneous coronary intervention along with general physicians, and an initiative to manage LDL-C using a region-wide LDL-C management clinical pathway (Figure 1) was launched in July 2022. The rate of intensive statin therapy at discharge increased from 34.5% to 79.8%, and the rate of patients achieving LDL-C <70 mg/dL at discharge increased from 37.2% to 54.6% following the implementation of the clinical pathway. However, the cost-effectiveness of implementing the clinical pathway remains to be determined. Purpose: The purpose of this study was to evaluate the cost-effectiveness of implementing the Nagasaki AMI Secondary Prevention Clinical Pathway. Methods: To evaluate the cost-effectiveness of implementing the clinical pathway compared with no implementation, a lifetime simulation was performed using mathematical models. The models consisted of a decision tree model to model the flow of the clinical pathway (Figure 2) and a Markov model to consider the risks of developing cardiovascular disease (CVD) events. The quality-adjusted life year (QALY) was used as the outcome. Drug costs and treatment costs for each CVD event were included. Drug costs were calculated from actual prescriptions. Treatment costs and utility scores for each event were based on the literature. The risk of each CVD event was calculated using baseline risks estimated using commercial claims data (DeSC Healthcare, Inc.) and patients' LDL-C levels at discharge and 1 month after discharge. LDL-C levels at each time point were set separately for the groups that achieved or did not achieve a discharge LDL-C < 70 mg/dL, for patients with and without implementing the clinical pathway. Results: Implementing the clinical pathway was evaluated as dominant, with an incremental gain of 0.079 QALYs per person and expected cost savings of JPY 103,124 per person. Implementing the clinical pathway was shown to not only provide additional health benefits by preventing CVD, but also to reduce future health care costs. In the analysis with a 10-year time horizon, the result remained dominant, and the same level of cost savings was expected. Conclusions: Implementing the Nagasaki AMI Secondary Prevention Clinical Pathway can be expected to reduce costs, in addition to increasing QALYs by preventing CVD. Further clinical and economic evaluation of long-term follow-up with a collaborative pathway to the general physician after discharge from the hospital is expected.