This paper presents a case of cardiac tamponade with idiopathic hemorrhagic pericarditis as the initial symptom of human immunodeficiency virus (HIV) infection. A 29-year-old male came to the emergency room with a sudden onset of dizziness. Upon arrival, he was hypotensive although not tachycardic, and his jugular venous pressure was not elevated. His chest X-rays revealed a mild cardiomegaly. Transthoracic echocardiography revealed a large amount of pericardial effusion with a diastolic collapse of the right ventricle, a dilated inferior vena cava with little change in respiration, and exaggerated respiratory variation of mitral inflow velocities, representing echocardiographic evidence of cardiac tamponade. After pericardiocentesis, his blood pressure improved to 110/70 mmHg without inotropics support. Serial 12-lead electrocardiograms during hospitalization revealed upwardly concave diffuse ST-segment elevation followed by a T-wave inversion suggestive of acute pericarditis. Pericardial fluid cytology and cultures for bacteria, mycobacteria, adenovirus, and fungus were all negative. HIV enzyme-linked immunosorbent assay (ELISA) was positive and confirmed by Western blot. The CD4 cell count was 168/mm3. Finally, the diagnosis of cardiac tamponade due to HIV-associated hemorrhagic pericarditis was made. It was concluded that HIV infection should be considered in the diagnosis of unexplained pericardial effusion or cardiac tamponade in Korea.