Deep venous thrombosis (DVT) in the upper extremities is a rare but important clinical illness, which leads to severe complications such as pulmonary embolism. Unlike DVT in the lower extremities, which is mainly induced by a hypercoagulable state, DVT in the upper extremities is usually caused by mechanical obstruction or anatomical stenosis in the venous system. We herein report a case in which DVT developed in the left upper limb during treatment of nephrotic syndrome. This is the first case report of upper-extremity DVT in association with nephrotic syndrome in the literature. Our patient was a 56-year-old male with nephrotic syndrome due to idiopathic membranous nephropathy who was treated with 40 mg/day of prednisolone. During corticosteroid therapy, he developed a swelling of the left upper limb. Computed tomography revealed thrombi in the left internal jugular vein and the left subclavian vein without anatomical abnormalities in his venous system. Thus, he was diagnosed with DVT of the upper extremities. After the initiation of warfarin treatment and subsequent regression of nephrotic syndrome, the swelling disappeared and the thrombi significantly diminished. DVT should be considered when upper-extremity edema is observed in patients with nephrotic syndrome.