A 49-year-old man complaining of pyrexia and dyspnea presented to our hospital with vital signs indicating shock, and his blood gas analysis showed hypoxia. Computed tomography of the chest showed lobar pneumonia of the left lingula. Severe community-acquired pneumonia with septic shock and acute respiratory failure was diagnosed. After admission to intensive care and being placed on mechanical ventilation, he was treated with imipenem/cilastatin (IPM/CS) and levofloxacin. Acinetobacter baumannii was detected by sputum and blood cultures. The A. baumannii showed susceptibility to IPM/CS, which was continued for 21 days. His systolic blood pressure during septic shock could not be sustained by initial treatment with noradrenaline, and vasopressin was immediately added. His blood pressure was barely sustained, and improvement of septic shock required 7 days. Moreover, mechanical ventilation was required for 37 days as a result of disuse syndrome after the A. baumannii pneumonia. He was finally discharged on the 97th hospital day, recovering from the complications. Because community-acquired A. baumannii pneumonia is very frequently accompanied by septic shock and acute respiratory failure, it may result in a fatal infection. Clinicians should be aware of this possibility and treat it with intensive therapies, including early use of appropriate antibiotics, vasopressors, and mechanical ventilation.