Pleomorphic-type anaplastic carcinoma of the pancreas is a rare and highly aggressive histological subtype of pancreatic ductal carcinoma. It is characterized by rapid progression and a poor prognosis. Preoperative diagnosis is often challenging due to nonspecific imaging findings and the frequent absence of elevated tumor markers. We present a resected case of pleomorphic-type anaplastic carcinoma of the pancreatic tail, which showed early recurrence in the remnant pancreas, potentially associated with a delayed-onset pancreatic fistula. A 63-year-old man presented with upper abdominal pain. Imaging revealed a cystic lesion in the pancreatic tail. Follow-up imaging showed enlargement of the lesion, and a retention cyst with possible underlying pancreatic carcinoma was suspected. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) was not performed due to concerns for cyst rupture. The patient underwent distal pancreatectomy with splenectomy. Histopathological examination confirmed pleomorphic-type anaplastic carcinoma. Although the drain was removed on postoperative day (POD) five due to low amylase levels in the drainage tube, a pancreatic fistula developed on POD 14, resulting in an intractable pancreatic fistula requiring persistent drainage. On POD 53, imaging revealed tumor recurrence in the remnant pancreas, along with peritoneal dissemination and right femoral bone metastasis. Retrospective evaluation of CT on POD 14 showed tumor recurrence compressing the main pancreatic duct, which was suspected to be the cause of the fistula. The patient declined further oncological treatment and died on POD 103. This case highlights the diagnostic and therapeutic challenges of pleomorphic-type anaplastic carcinoma of the pancreas. Early postoperative recurrence can lead to pancreatic stump disruption and the development of intractable pancreatic fistula.