The number of HIV-infected individuals susceptible to Hepatitis A virus (HAV) infection is increasing in Korea; however, it has proven difficult to devise a vaccination policy therefore because limited seroepidemiologic data exists for them. Accordingly, anti-HAV IgG was measured in 188 HIV-infected adults between July 2008 and July 2010. The nadir CD4+ T lymphocyte counts were not different between the HAV-positive and -negative groups (197 ± 138 vs 202 ± 129, P = 0.821). The only factor independently associated with seropositive status was age under 40 yr old (OR 0.017, P < 0.001). Our findings suggest that HAV vaccination in HIV-infected adults should be targeted at persons under the age of 40 yr.