Hospital malnutrition could be caused by not completing the food served in the hospital. This has been a big problem since it delays the recovery of the patient and extends the length of hospital stay. The purpose of the study was to reduce the plate waste for the DM diet by performing several nutrition service improvement activities. The study was performed in a general hospital with 900 beds. A questionnaire survey was taken by 39 DM patients to obtain their aspect of the hospital foodservice systems and the quality of the meals at the beginning of the study. The amounts of foods served in the hospital kitchen and returned were measured by weights. After the improvement activities, the measurement of the plate waste was performed again for comparison. The average percentage of plate waste for the DM diet was 23.2%. The survey showed no difference by sex, age or duration of admission in plate waste. However, this food wastage percentage showed differences between the patients having a chance to get information about the diet therapy (12.21%) and not having one(26.06%) (p < 0.05). Using a five-point Likert-type scale, the quality of food by its taste was 2.49 (1: very poor, 5: excellent), the temperature score was 3.56 (1: very poor, 5: excellent), and the amount of food served score was 2.95 (1: very poor, 5: excellent), and the preference score was 3.13 (1: very dislike, 5: very like). Nutritional care improving activities were performed by adjusting seasonings, developing new menus, and standardizing cooking methods in order to increase the satisfaction of meal quality. The dietitian's inpatients care protocol was adjusted to expand the nutritional counseling chance for the DM patients. After the improvement activities, the average plate waste was reduced to 14.6%, and the satisfaction of food taste and preference increased to 3.21 (p < 0.001), and 3.36 (p < 0.05) correspondingly. The result shows that, for therapeutic diet patients, food intake could be increased by improving the food service satisfaction by controlling the meal quality and clinical nutritional service activities.