Diffuse lipoblastomatosis is a rare lipomatous tumor of infancy that derives from fetal-embryonal fat. It usually affects infants and children and presents as a superficial mass that extends from the subcutis to the underlying muscle in the upper or lower extremities. In spite of its benign nature, the tumor may behave in a locally aggressive manner and invade the surrounding tissues. A case of isolated diffuse lipoblastomatosis of a 5-year-old boy in the plantar aspect of his right foot that has not been documented in that area before is described. The clinical and radiological presentation and histologic evaluation of diffuse lipoblastomatosis are discussed, in order to make a differential diagnosis between this rare tumor and other soft tissue tumors. In addition, the treatment principles of the tumor are described. This case demonstrates that diffuse lipoblastomatosis can be difficult to diagnose without histologic evaluation and, once diagnosed, should be treated by adequate surgical excision in order to prevent recurrence.