An 83-year-old Japanese man who underwent cholecystectomy for cholecystolithiasis 17 years ago visited our hospital owing to epigastric pain. He was initially diagnosed with choledocholithiasis and acute cholangitis following white blood cell, C-reactive protein, total bilirubin, alkaline phosphatase, and γ-glutamyltranspeptidase level elevations along with common bile duct stones on computed tomography (CT). Moreover, CT, magnetic resonance imaging, endoscopic retrograde cholangiography (ERC), and endoscopic ultrasonography (EUS) also revealed a 2-cm-diameter mass arising from the remnant cystic duct. The cytology of the bile at the time of ERC was not conclusive. However, EUS-assisted fine needle aspiration (EUS-FNA) of the mass confirmed the diagnosis of adenocarcinoma of the remnant cystic duct. The patient underwent extrahepatic bile duct resection. Cystic duct carcinoma following cholecystectomy is rare. We report a case diagnosed by EUS-FNA.