Summary Background Necrotizing fasciitis is a surgical emergency and old age is one of the predictors to mortality. Nonetheless, no specific report has addressed necrotizing fasciitis concerning aged patients. The aim of this study was to determine risk factors of mortality in elderly patients with necrotizing fasciitis. Methods A retrospective review of 65 patients with surgically confirmed necrotizing fasciitis in a tertiary medical center from January 2004 to December 2008 was conducted. Comparison between patients who survived and died was based on clinical findings, laboratory data, complications, and surgical timing. Results The mortality rate for the 65 patients was 32%. The average hospitalization was 33.7 days. Significant differences between the two groups were observed in surgical time, wound closure method, and admission levels of hemoglobin and albumin. Significant risk factors from binary logistic regression were liver cirrhosis, acute renal failure, and respiratory failure. Patients with more complications had a lower survival rate. Conclusion Early diagnosis of necrotizing fasciitis is difficult in aged patients, but in-hospital complications are the main determinants of mortality. Patients with liver cirrhosis are the high-risk group to mortality. Prevention of complications, such as acute renal failure and acute respiratory failure may be helpful in survival.