Gastrectomy is the most effective method of treating gastric cancer, but it is commonly associated with weight loss, nutritional deficiencies, and the increased risk of malnutrition due to post-surgery complications, including gastric stasis, dumping syndrome, malabsorption, and maldigestion. Malnutrition is a risk factor for postoperative complications and poor prognosis. To prevent it and guarantee a quick recovery after surgery, continuous and individualized nutrition intervention should be performed both before surgery and postoperatively. The Department of Dietetics at Samsung Medical Center (SMC) performed nutritional status assessment before gastrectomy, initial nutritional assessment within 24 hours of admission, description of therapeutic diet after surgery, nutrition counselling before discharge, and nutritional status assessment and individual nutrition counselling after 1, 3, 6, and 12 months from surgery. This is a case report of a patient who underwent gastrectomy as well as intensive nutrition intervention in SMC.