Intrapancreatic accessory spleen (IPAS) is a congenital abnormality, which mimics neoplasm. Distinguishing IPAS from pancreatic neoplasm/malignancy is extremely important from a treatment perspective. We report the case of a 67-year-old asymptomatic man who had a 1.3-cm, incidentally detected, pancreatic tail mass. The mass was round, well-circumscribed, and hypervascular with uniform enhancement. The image findings were highly suggestive of a pancreatic endocrine neoplasm. An endoscopic ultrasound-guided fine-needle aspiration was performed. Conventional smears revealed a polymorphous population of lymphocytes admixed with a subset of other inflammatory cells. Hematoxylin-eosin–stained cell block sections showed conspicuous thin-walled blood vessels in addition to inflammatory cells. Immunostaining for CD8 demonstrated strong positivity in endothelial cells of the thin-walled vessels. By correlating the cytologic findings with the result of immunostaining, we rendered the diagnosis of IPAS. Our experience supports the view that endoscopic ultrasound-guided fine-needle aspiration may enable a reliable, preoperative diagnosis of IPAS and thus prevent unnecessary surgery.