Herein, we encountered an 89-year-old woman with pancreatic cancer who presented with fever without infective focus, leukocytosis of 45,860 /microL, and elevation of serum granulocyte-colony stimulating factor (G-CSF). The patient could not receive any curative therapy due to an extremely aggressive clinical course. Specimens taken at necropsy revealed an adenosquamous carcinoma positive for G-CSF by immunohistochemistry; it was only the second reported case to date. She was finally diagnosed with G-CSF-producing pancreatic cancer. In light of the above, clinicians should consider the presence of G-CSF-producing tumors, including pancreatic cancer, when presented with patients showing leukocytosis of unknown origin and fever without infective focus.