Purpose Smoking cessation reduces morbidity and mortality of cardiovascular diseases. The purpose of this study was to evaluate the effect during smoking cessation treatment on glycemic control and cardiometabolic risk factors, including blood pressure and lipid levels, in patients with type 2 diabetes. Patients and Methods This retrospective cohort study included patients with type 2 diabetes who participated in a smoking cessation program, which comprised health education and medication prescription at an outpatient clinic in combination with a 3-month follow-up by phone. Data on patient background characteristics, cardiometabolic factors, smoking status, body weight, and body mass index before and after the program were collected for analysis. Results The analysis included 241 participants with an average age of 58.6 ± 10.6 years. The rate of successful cessation at three months was 34.0%. Compared with the baseline levels, there were significant decreases in the levels of fasting plasma glucose (10.0 ± 46.8 mg/dL, P = 0.001), HbA1c (0.3 ± 1.4%, P = 0.004), systolic blood pressure (4.6 ± 17.5 mmHg, P < 0.001), diastolic blood pressure (2.9 ± 11.3 mmHg, P < 0.001), and total cholesterol (7.9 ± 42.8 mg/dL, P = 0.020) after participation in the smoking cessation program while there was no significant difference in body weight (0.1 ± 1.2 kg, P = 0.444). After adjustment for covariates, the decreases in HbA1c and total cholesterol levels were significantly better in younger participants and higher baseline nicotine dependence scores were associated with decreases in the levels of blood pressure, fasting plasma glucose, and triglycerides. However, the decrease in smoking amount was not associated with the changes in cardiometabolic factors. Conclusion Participation in a smoking cessation program was associated with improvements in glycemic control and cardiometabolic risk factors in patients with type 2 diabetes. The observed improvements were associated with participation in the program but not with the decrease in smoking amount.