Background: Tumor-induced osteomalacia (TIO) is a rare, tumor-induced, metabolic bone disorder, the exact incidence of which is unknown. The most common cause of TIO is hypersecretion of tumor-derived fibroblast growth factor 23 (FGF23). Surgical resection can cure TIO in most cases, while for patients with TIO who are ineligible for surgery, biologic antibodies targeting FGF23 can be used as treatment. However, the diagnosis of TIO is more difficult than its treatment as the initial presentation can be misleading or nonspecific; thus, diagnosing TIO remains a clinical challenge. Case Description: Herein, we present a case of TIO originating from the nasal cavity neoplasm in which the patient also had a rare, thymic-derived, tumorous lesion. A diagnosis of osteoporosis was subsequently made, and a disorder of phosphorus metabolism was discovered. After determining that the patient was exhibiting signs of TIO, we used gallium-68 dotatate positron emission tomography/computed tomography (68Ga-DOTATATE PET/CT) to locate the tumor position. Conclusions: This case report emphasizes the importance of electrolyte testing, which is potentially helpful for quickly identifying the presence of disorders of phosphorus metabolism in suspected patients. Subsequently, appropriate imaging techniques (e.g., 68Ga-DOTATATE PET/CT) should be used to identify potential TIO lesions. Most patients with TIO can be treated successfully following diagnosis.