Classic Lemierre syndrome is a septic internal jugular venous thrombophlebitis secondary to oropharyngeal anaerobic infection in adolescents and young adults. Upper respiratory tract infection is the most common antecedent. We report a case of Lemierre syndrome as a rare infectious disease. A 20-year-old man complained of high fever, right neck discomfort and chest pain. Chest X-ray revealed infiltrative shadows, suggesting bacterial pneumonia. Although cefcapene pivoxil hydrochloride hydrate (CFPN-PI) was given in a local clinic, his symptoms did not improve. Then he was referred to our hospital. Chest CT findings showed bilateral multiple nodular shadows with small cavities, suggesting septic embolization. Fusobacterium necrophorum was cultured from specimen of the blood, and an enhanced neck CT scan showed thrombosis in the right internal jugular vein. These findings led us to a diagnosis of Lemierre syndrome. Four weeks of antibiotics and anticoagulants ameliorated inflammatory findings in blood, but internal jugular vein thrombosis remained. Currently, there is no consensus opinion on the use of anticoagulation in patients with Lemierre syndrome complicated by septic internal jugular thrombosis and embolism. Early and effective antibiotics therapy may prevent the development of the syndrome and its associated complication, although it is unclear whether the outcome will be favorable.