Background: Type 2 diabetes mellitus (T2DM) is the most common type of diabetes mellitus (DM) and its prevalence in China has increased rapidly. Poor control of DM leads to a series of complications, which seriously impair patients' quality of life. Importantly, the proportion of T2DM patients who meet the diagnostic criteria for metabolic syndrome (MS) is very high. The coexistence of the two diseases increases DM complications and the incidence of cardiovascular and cerebrovascular diseases. Individuals that have T2DM and MS experience a higher incidence of depression and anxiety symptoms than the general population. These negative emotions create obstacles in effectively managing blood glucose levels. In addition, T2DM and MS patients commonly display suboptimal self-care behaviors, which can be attributed to negative emotions, insufficient knowledge about diabetes, or cognitive biases linked to the disease. Cognitive behavioral therapy (CBT) aims to change the non-adaptive cognitions and behaviors of patients by developing therapeutic alliances, psychological education, cognitive reconstruction, and behavioral activation. Previous studies have applied it to the prevention and treatment of DM and MS and found positive effects. However, there have been few studies on the coexistence of two or more conditions. To address this gap, this study aimed to conduct a randomized controlled trial (RCT) to explore the effectiveness of CBT on the improvement of health outcomes in T2DM patients who have comorbid MS. This study represents the pioneering effort to explore the effectiveness of CBT in diabetes patients with coexisting MS. Additionally, the innovative integration of both face-to-face and remote intervention methods adds a novel dimension to this research. Furthermore, the study encompasses a diverse array of health outcome, including physiological indicators, psychological indicators, behavioral indicators, quality of life, and sleep quality. Aims: This study had three primary objectives: (1) to evaluate the effectiveness of CBT in improving health outcomes for patients who have diabetes, hypertension, and coronary heart disease (CHD) using existing published studies, (2) to use baseline data to identify the variables that may be related to emotions, behaviors, and cognition in patients who have T2DM and comorbid MS to design targeted CBT intervention programs for the cohort of patients who have T2DM and comorbid MS, and (3) to investigate the impact of the CBT intervention program designed for this study on physiological, psychological, and behavioral indicators as well as its influence on sleep quality and the overall quality of life of patients who have T2DM and comorbid MS.