This study aimed to compare the effects of activity-based personalized nutrition education (APNE) with a general instruction for diabetes (control, CTRL) in middle-aged and older Korean outpatients with type 2 diabetes. After an initial screening, 70 subjects were randomly assigned to APNE (n = 37) or CTRL (n = 33) group. APNE considered each patient’s anthropometry, blood chemistry data, and dietary habits in addition to planning meal choices with the aid of registered dietitians. After 3 months, dietary behavior, food intake, and anthropometric and blood measurement results were evaluated. Fasting blood glucose, 2-hour postprandial blood glucose, and glycated hemoglobin levels decreased in the APNE group (n = 33) but not in the CTRL group (n = 23). In the APNE group, the meal intervals and number of days of consuming high-fat food were decreased, while the number of days following a meal plan and balanced diet that entailed consuming fruits, vegetables, and healthy food was increased. A lower consumption of carbohydrates, saccharides, grains, and tuber crops and a higher protein, pulses, and fat-derived calorie intake compared with the initial values were observed in the APNE group. In contrast, only the number of days following the meal plan and balanced diet was increased in the CRTL group, without significantly changing the individual macronutrient-derived calorie intake. The APNE approach appeared to effectively educate outpatients with type 2 diabetes about changing their dietary behavior and food intake and improving the clinical parameters related to diabetic conditions.