BACKGROUND A part of hypercalcemia is a paraneoplastic syndrome. Its association with lymph node metastasis of bladder cancer has been infrequently reported in the literature. METHODS A 75-year-old male presented with gross hematuria and was diagnosed with bladder cancer without metastasis. Following neoadjuvant chemotherapy, radical cystectomy was performed. The surgical margin was negative. The bladder cancer was classified as pT3bN0 and mainly constituted squamous differentiated urothelial carcinoma and sarcomatoid variant. His perioperative serum calcium levels were normal. At 6 months of surgery, computed tomography revealed lymph node enlargement, and additional 2 weeks later, he developed epileptic seizures with a serum corrected calcium level of 18.7 mg/dL. He was diagnosed with hypercalcemia caused by the lymph node metastasis of bladder cancer. Despite receiving several supportive therapies for 22 days, he died. CONCLUSIONS Hypercalcemia associated with bladder cancer is highly resistant to existing therapy, particularly when caused by cancer metastasis.