Warthin's tumor (WT), so-called adenolymphoma, is a benign salivary gland tumor with both epithelial and lymphoid histological characteristics, so the histogenesis remains unclear. Treatment consists primarily of tumor removal or conservative follow up. Here we present a rare case of malignant lymphoma arising from heterotopic (ectopic) WT. A 102-year-old man presented with a mass in the left side of the neck which was painless but gradually enlarged over 1 month. The mass was 2-3 cm in diameter, and freely moveable below the angle of the mandible. The mass was totally removed. The histological diagnosis was malignant lymphoma, diffuse large B-cell type, arising from heterotopic WT. Postoperative staging examination including chest radiography, bone scan, and computed tomography of the abdomen and pelvis revealed no evidence of dissemination of malignant lymphoma. Malignant transformation within WT is rarer in the lymphoid component than in the epithelial component. Only 16 cases of malignant transformation arising from WT have been reported, including only three cases of non-Hodgkin lymphoma apparently arising from heterotopic WT. Tumor removal or careful follow up is recommended in patients with WT because of the potential risk posed by such malignant transformation.