Acute acalculous cholecystitis (AAC) still remains one of the most elusive diagnoses and occurs in various conditions. Although AACs caused by viral infections are rare, various viruses have been revealed to cause AAC. Here we present a case in which a man suffered from AAC caused by a Hantaan virus infection. A 35-year-old man was referred to the emergency room for myalgia and fever that began 4 days ago. He suffered oliguria and abdominal pain for 2 days. At the time of his visit to the emergency room, he experienced a fever that spiked up to 38.3℃. An initial blood sample objectified the following pathologic results: white blood cells - 10260/µl; C-reactive protein - 6.76 mg/dl; total bilirubin - 1.7 mg/dl; AST - 90 IU/L; ALT - 233 IU/L. In the computed tomography, bilateral perirenal fluid collections and bilateral flexural effusion were shown and acute hepatopathy and cholecystopathy were also shown. Because there was no definite tenderness around the patient's right upper quadrant from physical examination and his cholecystopathy looked like it was from secondary change according to acute hepatopathy, we decided to perform conservative care without surgical treatment. The following day, in viral antibody test, Hantaan virus antibody was detected. After conservative management, the patient's condition improved and his laboratory findings were stable. The patient was discharged on the 10th day at the hospital stay without any symptoms. The Hantaan virus infection should be suspected as a causative agent of AAC, especially when there is abnormal liver function tests and abdominal pain.