Here, we report a case of successful surgical resection of expansive-growth acinar cell carcinoma. A 59-year-old man was referred to a local hospital with abdominal distention. CT revealed a large abdominal tumor. Subsequently, he was referred to our hospital. Physical examination showed a large tumor on his left upper abdomen without tenderness. CT revealed an enhanced 18 cm-sized expansive-growth tumor on the left flank, suggesting a primary pancreatic tumor. EUS-FNA yielded a diagnosis of adenocarcinoma. Imaging findings were not typical for pancreatic ductal carcinoma. We performed distal pancreatectomy with splenectomy, transverse colon resection, and proximal gastrectomy. Pathological findings revealed a tumor, measuring 19.5×16.5×15.5 cm, originating from the pancreatic body, positive for trypsin, chymotrypsin, and elastase, consistent with a diagnosis of acinar cell carcinoma, pT3, N0, M0. Four courses of adjuvant chemotherapy with S-1 were provided, and the patient is currently alive without recurrence for 10 months.