A 62-year-old man was admitted to our hospital for dysphagia, leukocytosis, and pyrexia. The serum level of granulocyte colony-stimulating factor (G-CSF) was high and immunostaining of a biopsy specimen of esophageal tumor using anti-granulocyte-macrophage colony-stimulating factor (anti-GM-CSF) antibody demonstrated GM-CSF expression in the cytoplasm of the tumor cells. After esophagectomy, the leukocyte count and serum G-CSF level normalized. Histologically, this tumor was diagnosed as a carcinosarcoma with two components: squamous cell carcinoma and sarcoma. Tumor cells were also positive for G-CSF receptor, suggesting autocrine growth regulation by G-CSF. Moreover, tumor cells were positive for Ki-67, cyclin D1, p53, and epidermal growth factor receptor (EGFR), which were related to the acquisition of more aggressive tumor behavior. Although G-CSF-producing esophageal carcinosarcoma is very rare, we should consider such disease when a patient has symptoms of leukemia such as leukocytosis and high fever.