Internal jugular vein thrombosis is usually associated with intravenous drug abuse, long-term venous catheterization, local infection, or spontaneous occlusion. The antiphospholipid syndrome is now recognized as one of the commonest causes of acquired arterial or venous thrombosis. Lemierre's syndrome is an uncommon but potentially lethal complication of internal jugular vein thrombosis after an oropharyngeal infection. A 34-year-old man presented with fever and progressive, painful right neck swelling 6 days after an episode of pharyngitis. Clinical studies including radiological and laboratory tests confirmed the diagnosis of Lemierre's syndrome associated with antiphospholipid syndrome. Although Lemierre's syndrome is a well-known cause of internal jugular vein thrombosis, association with antiphospholipid syndrome is very rare.