A 26-year-old man, who had untreated gingivitis for several months, was treated with antibiotics levofloxacin because of acute adenoiditis with fever and sore throat. Several days later, he presented impetigo, dyspnea, and back pain and was referred to our hospital. A chest radiograph image and computed tomography showed multiple nodular infiltrates in both peripheral lung fields and a thrombus in the left jugular vein. These findings indicated the diagnosis of Lemierre's syndrome with septic pulmonary emboli, although no pathogen was detected in the blood culture. Porphyromonas asaccharolytica was detected by culture obtained from the impetigo, and the patient was successfully treated with antibiotics, including a high dose of ampicillin and warfarin therapy. We reported here a rare case of Lemierre's syndrome presenting with impetigo as an uncommon manifestation of this syndrome.