The number of symptomatic hepatitis A cases has progressively been increasing during the last several years in Korea. Available cost estimates indicate a growing burden to the public. The purpose of this study was to determine the extent of treatment costs for patients with hepatitis A and to analyze the influential factors with nationwide data. We collected data on 72,921 patients with hepatitis A from 5-year National Health Insurance claim archives between 2004 and 2008. Multiple regression analyses were conducted to examine influential factors affecting treatment costs for hepatitis A. Total treatment costs for patients with hepatitis A during the 5-year period were US$47,902,087 and increased significantly each year. In total, 91.4% of treatment costs were used for hospitalization, and the proportion of inpatients increased gradually throughout the study period. The most influential factor on treatment costs was treatment duration. Our results show that the soaring number of patients with hepatitis A followed by the hospitalization-focused treatment practice is a major factor associated with the rapid increase in treatment costs. Appropriate policies should be promptly developed to control treatment costs and economic burden of hepatitis A infections.