Background: Pheochromocytomas originate from chromaffin cells of the adrenal medulla, resulting in excessive production of catecholamines and bizarre clinical symptoms. An extra-adrenal pheochromocytoma is called a paraganglioma. Urinary bladder paraganglioma represents an uncommon tumor that accounts for <0.05% of all bladder tumors. Case presentation: Presented here are three cases of incidental urinary bladder paraganglioma, all having hematuria as the primary symptom. During transurethral resection of bladder tumor, blood pressure fluctuated intensely with profuse bleeding, leading to the abandonment of the procedure. The patients were later diagnosed as having paraganglioma, and then, they were subjected to systemic evaluation and definitive treatment. Conclusion: Although bladder paraganglioma is a rare condition, it should be strongly suspected if a patient who has no definitive symptoms of the disease developed a sudden hemodynamic change at the very start of the procedure.