A person diagnosed with acquired immunodeficiency syndrome in 2000 and who received highly active antiretroviral therapy developed co-infection with dengue virus in 2003. In the course of the co-infection, he developed fever, thrombocytopenia (13,700 cells/mm3), petechia, and hypoalbuminemia, which are compatible with the World Health Organization criteria for a case of dengue hemorrhagic fever. Human immunodeficiency virus was not detected 30 days before co-infection and 10 days afterwards. His CD4 cell count did not show significant alterations in the two periods evaluated. He continued his course of treatment without arterial hypotension, serious hemorrhage, or other life-threatening complications.