BACKGROUND Paraneoplastic hypercalcemia is a well-described complication associated with a variety of malignancies. However, its incidence in gynecological malignancies is low. CASE REPORT A 53-year-old woman presented with progressive abdominal distention and irregular vaginal bleeding of several weeks' duration. A contrast CT abdomen and pelvis was significant for a mass in the lower uterine/cervical region, multiple peritoneal and omental masses, enlarged pelvic and paraaortic lymph nodes, and large-volume ascites. A pelvic exam revealed a fungating vaginal mass, with biopsy showing a high-grade tumor with immunohistochemical staining positive for vimentin, CD10, and cyclin D1, consistent with endometrial stromal sarcoma. During her hospitalization, the patient became increasingly lethargic. Workup showed severe hypercalcemia and evidence of acute kidney injury. The patient did not have evidence of bony metastatic disease on imaging studies. Further laboratory evaluation revealed an elevated PTHrP of 301 pg/mL (nl 14-27), a depressed PTH level of 3 pg/mL (nl 15-65), and a depressed 25-OH vitamin D level of 16 ng/mL (nl 30-100), consistent with humoral hypercalcemia of malignancy. The patient was treated with pamidronate, calcitonin, and intravenous fluids. She eventually required temporary hemodialysis and denosumab for refractory hypercalcemia, which improved her electrolyte abnormalities and clinical status. CONCLUSIONS Uterine malignancies of various histologies are increasingly recognized as a cause of humoral hypercalcemia. They are an important differential diagnosis in a woman with hypercalcemia and abnormal vaginal bleeding or abdominal symptoms.