Paraganglioma, a sporadically occurring rare tumor should be included in the differential diagnosis of retroperitoneal tumors, such as malignant lymphomas, gastrointestinal stromal tumors, sarcoma and carcinoma of unknown primary site. A 58-year-old Japanese woman presented with a large retroperitoneal tumor detected by ultrasonography (US). She had no medical history of hypertension. Computed tomography showed a mass, 7 cm in diameter, located between the pancreas and the inferior vena cava. It was unclear whether the mass originated from the duodenum or the mesentery. Endoscopic ultrasonography (EUS) demonstrated a large solid paraduodenal mass. Doppler US revealed sparse vascularity in the tumor. With the differential diagnosis of retroperitoneal tumor, we carried out EUS-FNA. At the time of the third needle puncture, transient severe hypertension was noted, with a blood pressure measurement of 269/130 mmHg. Data obtained from urine and blood examinations after EUS-fine-needle aspiration indicated a diagnosis of paraganglioma.