Kaposiform hemangioendothelioma (KHE) is a rare, locally aggressive, vascular spindle-cell proliferation, with resemblance to Kaposi sarcoma. Usually, this tumor occurs in the skin and the retroperitoneum. We described a girl with a kidney localization and extension into the inferior vena cava and even into the right atrium. The case presented here is unique in 2 ways. First, kidney involvement of KHE has never been described in the literature until now. Second, and most remarkably, extensive tumor thrombosis suggests surgical excision even with cardiopulmonary bypass. The KHE of the kidney is a rare tumor but should be taken into account in the differential diagnosis with other pediatric renal neoplasms.