Skipping breakfast or irregular breakfast is associated with poor glycemic control. However, a relationship between the timing of dinner and glycemic control in people with type 2 diabetes remains indefinite. Therefore, we investigated the relationship between late-night-dinner and glycemic control in people with type 2 diabetes. We performed questionnaire survey for lifestyle factors in this cross-sectional study. We defined having dinner later than eight pm as late-night-dinner. We examined the differences in clinical and metabolic parameters between those who have late-night-dinner and those who do not have. We also examined the relationship between late-night-dinner and HbA1c, using multiple regression analysis. Ninety-five people (23.2%) had a late-night-dinner, among 409 people with type 2 diabetes. Metabolic parameters (mean (SD) or median (interquartile range)) of people with late-night-dinner were worse than those of without, including body mass index (BMI) (24.4 (4.0) vs. 23.2 (3.4) kg/m2, p = 0.006), triglycerides (1.5 (1.1-2.1) vs. 1.2 (0.8-1.7) mmol/L, p < 0.001), HDL-cholesterol (1.4 (0.4) vs. 1.6 (0.4) mmol/L, p = 0.004) and hemoglobin A1c (58.1 (13.3) vs. 55.2 (10.2) mmol/mol, (7.5 (1.2) vs. 7.2 (0.9) %), p = 0.023)). Late-night-dinner (standardized regression coefficient = 0.13, p = 0.028) was associated with hemoglobin A1c after adjusting for age, BMI, sex, duration of diabetes, smoking, exercise, alcohol, snacking after dinner, nighttime sleep duration, time from dinner to bedtime, skipping breakfast, and medication for diabetes. Late-night-dinner is independently associated with poor glycemic control in people with type 2 diabetes.