Pseudoaneurysm of the cystic artery is rare; to our knowledge, fewer than 30 cases have been reported worldwide. We report the first case of an unruptured pseudoaneurysm of the cystic artery with concurrent acute calculous cholecystitis. We incidentally detected the aneurysm by contrast-enhanced computed tomography (CT) in the edematous, thickened wall of the gallbladder neck in a 71-year-old man, whereas in most of the reported cases the disease presented as hemobilia. Because of the high risk of aneurysm rupture in this location, we avoided such interventions as percutaneous cholecystostomy and laparoscopic cholecystectomy. The aneurysm was localized pathologically in the undisrupted gallbladder wall, and elective open cholecystectomy with ligation of the cystic artery was performed successfully. Our case highlights the usefulness of CT for both diagnosis and patient management. Open cholecystectomy with ligation of the cystic artery is demonstrated as a reasonable first line of treatment for this unusual condition.