The objective of this study was to investigate the clinical efficacy of parenteral nutrition (PN) as supplemental feeding for patients with anorexia nervosa (AN). This study was conducted by reviewing the medical records of patients with AN who were hospitalized at a non-specialized ward. A total of 129 patients with AN were recruited, consisting of 67 patients received PN with oral refeeding and 62 patients received oral refeeding alone. We compared the weight gain at discharge and after discharge between the groups. As a result, at admission, the patients given supplementary PN had lower body mass indices and lower caloric intake than the patients without PN. The mean duration of PN was 8.5 days, which amounted to about a third of the average hospital stay with no difference between the groups. Both groups had similar weight gains during hospitalization, but the patients with PN had higher weight gains than the patients without PN at one and three months after discharge. In conclusion, the results suggest that supplementary PN in the early stage of refeeding might initiate weight gain in AN when nasogastric tube feeding is not possible. Randomized controlled trials are needed to be further tested of PN in treatment of AN.