Lupus anticoagulant-hypoprothrombinemia syndrome (LAHS) is a rare disease associated with lupus anticoagulant and factor II deficiency. LAHS is usually associated with autoimmune disease or with transient viral infection. A 27-month-old boy had a gross hematuria. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) were markedly prolonged. The aPTT was not corrected after mixing with normal plasma. The level of factor II was decreased. Diluted Russell's viper venom test demonstrated the lupus anticoagulant. He was diagnosed with LAHS. His clinical symptom was improving without medical treatment. Serial laboratory studies showed that PT, aPTT, and factor II level were normalized.