Background: The Pay-for-performance (P4P) program of diabetes care has demonstrated successful outcomes in patients with type 2 diabetes. However, the effectiveness of this multidisciplinary care model for psychiatric patients has never been evaluated. The objective of this study is to examine the effectiveness of P4P program of diabetes for psychiatric patients with diabetes. Methods: This study utilized a retrospective cohort design to examine the effectiveness of P4P program of diabetes care for psychiatric patients with diabetes. The participants’ HbA1c (hemoglobin A1c) data of the fourth quarter in 2018 were used as baseline value, while P4P program was not applied yet. HbA1c data of every quarter in 2019 were collected. Generalized estimating equations (GEE) was used to analyze the change of HbA1c level. Results: The HbA1c level increased slightly in the first quarter, and then decreased gradually since the second quarter. The HbA1c level was significantly lower in the fourth quarter after P4P program intervention (p < 0.05). Conclusion: P4P program of diabetes care is also effective on psychiatric patients with diabetes, and this multidisciplinary care model could be encouraged and promoted for psychiatric patients with diabetes.