Macrocystic serous cystadenoma is an unusual and essentially benign pancreatic tumor. Ages of reported cases are usually 60 years and over, with a mean age of 54 years. Herein, we report on a 26-year-old man who presented with upper abdominal pain. A cystic lesion in the mid-portion of the pancreas was revealed by abdominal computed tomography, and a pseudocyst was suspected. A distal pancreatectomy was performed with a splenectomy due to intractable abdominal pain and being unable to rule out to be a mucinous cystic neoplasm, which has a malignant potential. The histopathological diagnosis was macrocystic serous cystadenoma of the pancreas. To our knowledge, this patient is the youngest person to present with such tumor. Clinical and pathologic features including complete immunohistochemical studies are presented, and we review the relevant literature.