Idiopathic thrombocytopenic purpura (ITP) preceding malignant lymphoma is a rare condition. Most cases occur simultaneously with lymphoma or after it has been diagnosed. The case of a child with idiopathic thrombocytopenic purpura recovered after prednisolone treatment, but lymphoma developed four months later. The pathogenesis for idiopathic thrombocytopenic purpura evolving into malignant lymphoma is still unknown and further study is necessary.