Hepatic flares occurred in two patients with HBV/HIV coinfection following the commencement of antiretroviral therapy (ART). At that time, the HIV RNA and HBV DNA levels had decreased. The results of liver biopsies showed lymphocytic infiltration that was diffusely positive for CD8(+) T cells in the portal areas and lobules. These findings suggested HBV-related immune reconstitution inflammatory syndrome (IRIS). The alanine aminotransferase levels of both patients gradually decreased with the continuation of ART. Because there are few reports of the liver histology of HBV-related IRIS, these cases provide a better understanding of the pathogenesis of HBV-related IRIS.