Hemophagocytic syndrome (HPS) is an unrecognized complication occurring in the acute stage of human immunodeficiency virus (HIV) infection that is seldom reported in the literature. We herein present a case of HPS that occurred during the seroconversion stage of HIV infection. In this case, pancytopenia and liver dysfunction related to HPS recovered after the initiation of antiretroviral therapy (ART). This report indicates the importance of early recognition of HPS and suggests that prompt initiation of ART has the potential to control HPS in the acute stage of HIV infection.