A case of pseudoaneurysm that is a rare complication of shoulder arthroscopy is reported. A 73-year-old man with rotator cuff tear underwent arthroscopic rotator cuff repair. On post-operative day 3, a pulsating mass (diameter 5 mm) was detected near the anterior portal. Then, the mass gradually enlarged, which was diagnosed as pseudoaneurysm. After the consultation with vascular surgeons, the mass was surgically excised following ligation of feeding artery 6 weeks after the arthroscopic surgery. Thus far, no recurrence has been observed. Level of evidence V.