We report a case of acquired thrombotic thrombocytopenic purpura (TTP) triggered by influenza A virus subtype H1N1 infection. In December 2010, a 27-year-old man was diagnosed with pneumonia from influenza A virus infection at a local clinic. Two days later, he was admitted to our hospital because of a worsening condition and unexplained thrombocytopenia. The influenza A virus subtype H1N1 real-time polymerase chain reaction test was positive. The patient had typical clinical signs of TTP, thus he was diagnosed with TTP. He received treatment with oseltamivir and high dose methylprednisolone. Plasma exchange therapy was started daily at a 1.5 dose volume of his whole blood. After the 17th plasma exchange therapy, the symptoms and abnormal laboratory results had recovered to normal. Finally, 47 days after admission, the patient had recovered completely and was discharged. This case suggests that the influenza A virus subtype H1N1 infection may have triggered acquired TTP.