We investigated the effect of a nutrition education tool using self-monitoring of blood glucose on glycemic control in overweight or obese people with prediabetes. Of 31 non- treated male participants aged 20 - 69 years, those with HbA1c of 5.6%- 6.5% and a body mass index of 24 kg/m² or higher were randomly cluster allocated. The intervention group performed self-monitoring of blood glucose 2 hours after supper twice a week for 6 months and both groups underwent nutrition education on the association between meals and postprandial blood glucose once every 2 months. Fifteen and 16 participants were enrolled in the intervention and control groups and 11 and 10 participants completed this study. Glycated hemoglobin did not show a significant difference in the change after this intervention study between the intervention group and control groups (p=0.09). There was no significant difference in BMI. Mean proportions of carbohydrate comprising total energy intake tended to increase in the intervention group (p=0.06). In the intervention group, the sense of control over internal temptation was improved (p=0.01). Regarding the knowledge and behavior of portion size of food, significant improvements after intervention were shown in both the intervention group and the control group (p=0.02, p=0.01). It was clarified that the combined use of SMBG and this nutrition education tool can help people to understand the appropriate amount of macronutrients and food groups per meal, and the impacts of macronutrients on increasing blood glucose levels. It is suggested that reflection on behavior and improvement of problems would increase self-efficacy and lead to positive behavioral change.