Objective: The purpose of this study was to investigate the relationship between changes in nutritional status and postoperative outcome among cardiac surgery patients following nutritional support. Patients and Methods: The study used a follow-up method. Twenty-six Malnourished subjects who underwent cardiac surgery at medical centers in Taipei were recruited by purposive sampling. These patients were evaluated periodically with respect to their nutritional index and prognostic index during the post-operative hospitalization period. Results: Major findings of this study were as follows: 1. The percentage of patients with ideal body weight among patients showed a marked increase during post-nutritional support weeks 1 and 2 (p＜0.01). 2. The patient's mid-arm circumferences decreased during post-nutritional support weeks 1 and 2 compared with pre-op averages, but a rebound was observed from week 1 to week 2 (p＜0.05). 3. Serum albumin, hematocrit and total lymphocytes at 2 weeks after the initiation of nutritional support were significantly higher in surviving than in deceased patients. 4. The average caloric intake during post-op week 1 was not significantly correlated with the post-operative prognostic indices, while that of post-op week 2 was negatively correlated with the number of post-op hospitalization days (p＜0.01) as well as length of post-op bed-ridden time )p＜0.01). Conculsions: These results indicate that untritional support can improve the outcome of malnourished cardiac surgery patients and significantly increase the survival rate in the early post-operative period. This study can serve as a useful reference in clinical practice.