A 61-year-old man was hospitalized for creating vascular access for maintenance hemodialysis. Chronic interstitial nephritis was the cause of his end-stage kidney disease. An arteriovenous graft (AVG) was selected because superficial veins in his bilateral upper limbs were not suitable for arteriovenous fistula (AVF). Venography did not show any stenotic lesions in the drainage veins bilaterally. Soon after creation of the AVG, his left arm began to swell. Obstruction of the drainage vessels downstream of the AVG was highly suspected. Magnetic resonance imaging disclosed that the left brachiocephalic vein was compressed at the junction of the superior vena cava by a mediastinal cystic tumor. This tumor was 15 mm in diameter and was tentatively diagnosed as a bronchogenic cyst. While initiating hemodialysis using the AVG, the patient's body weight was decreased by the extracorporeal ultrafiltration method, followed by amelioration of swelling in the left arm. Because the swelling and pain of his left upper limb gradually subsided, we finally decided not to close the AVG and continued hemodialysis using the left AVG. He is currently on maintenance hemodialysis for 3 months with a slightly swollen left upper limb. Central venous obstruction or compression is one of the major causes of ipsilateral limb swelling in patients on hemodialysis. Central venous stenosis caused by previous central catheter insertion is often involved. Our case emphasizes the importance of searching for potential anatomical obstruction of drainage vessels by mediastinal tumors as a potential cause of venous hypertension in hemodialysis patients.