Granulocyte colony-stimulating factor (G-CSF)-producing urothelial carcinomas (UCs) are rare and have a poor prognosis. According to the literature, treatment for G-CSF-producing UCs is very difficult. We experienced 2 cases of UC presenting with leukocytosis. In these cases, serum G-CSF levels were higher than the reference value with leukocytosis at diagnosis, and the resected specimens were positive for anti-G-CSF immunostaining. One case had a good prognosis and the other case died after 9 months from diagnosis. A change in serum G-CSF levels was reportedly an effective tumor marker in several reports. In the present cases, evaluation of serum G-CSF levels was found to be more sensitive than computerized tomography. The treatment and outcomes of UC-producing G-CSFs and the efficacy of serum G-CSF as a tumor marker are discussed based on our cases and a review of the literature.