Pituitary metastasis occurs rarely in cancer patients and often remains undiagnosed. However, early detection and appropriate treatment can improve the patient's quality of life and possibly prolong survival. Herein, we describe the case of a 52-year-old woman with panhypopituitarism caused by metastases to the hypothalamus and pituitary from primary breast cancer. She had a 5-year history of breast cancer with metastases to the bones 1.5 years after initial diagnosis and mastectomy. She presented with severe headaches, generalized fatigue, dizziness, hypotension, difficulties with balance and coordination, polyuria, and polydipsia. Laboratory work-up revealed panhypopituitarism (central diabetes insipidus; hypothyroidism; and low prolactin, gonadotrophin, and adrenocorticotropic hormone levels), and magnetic resonance imaging confirmed the pituitary and hypothalamic involvement. She received hormone replacement therapy, radiation therapy of the sella turcica and suprasellar lesion, and chemotherapy, with significant improvement of her clinical status, but she died 15 months later.