We report a case of Q fever-related antiphospholipid syndrome in a patient presenting with acalculous cholecystitis and pneumonia. Serial laboratory tests indicated that the previous serological tests suggesting hepatitis C virus and Mycoplasma pneumoniae infections were false-positives. The patient's fever persisted despite treatment with doxycycline, but disappeared 1 day after initiation of steroid treatment. To avoid incorrect diagnosis and subsequent delays in appropriate treatment of Q fever patients, the possibility that Q fever can masquerade as other infections or as an autoimmune disease should be kept in mind.