Oncogenic osteomalacia is a rare paraneoplastic syndrome that occurs secondary to tumor development in a variety of locations. Only about 140 cases have been reported in the literature. The most common causal tumor is phosphaturic mesenchymal tumor (PMT), a histologically benign lesion. The two most common sites of PMT are the lower extremities and the head/neck. We report the case of a 33-year-old woman with oncogenic osteomalacia who was diagnosed with two PMTs; the first arose in the tibia, and the second occurred 2 years later in the maxillary sinus. To the best of our knowledge, this is the first reported case of multiple PMTs. Despite resection of both tumors, the patient's signs and symptoms did not resolve, suggesting either incomplete tumor removal or the presence of another undetected tumor. We discuss the diagnosis of oncogenic osteomalacia, its associated biochemical abnormalities, and its histopathology.