This study aimed to clarify the efficacy and toxicity of first-line combination treatment with paclitaxel, cisplatin, and gemcitabine (PCG) for advanced/metastatic urothelial carcinoma (UC) in cisplatin-unfit patients compared with cisplatin-fit patients. We conducted a retrospective study of patients who received first-line PCG. Using international consensus criteria, patients were classified into cisplatin-fit and -unfit groups. Cisplatin-unfit patients received PCG with adjustment of the cisplatin dose after assessing 24-hour urinary creatinine clearance, without modifying the administration interval. From 2008 to 2017, 50 patients received first-line PCG, of whom 30 and 20 were classified into the cisplatin-fit and -unfit groups. After a median follow-up of 15.0 months, the median overall survival (OS) and progression-free survival (PFS) were 15.0 and 9.8 months in all patients, 15.0 and 10.0 months in the cisplatin-fit group, and 13.2 and 9.3 months in the cisplatin-unfit group, respectively. There was no significant difference in OS (hazard ratio [HR]: 1.33, 95% confidence interval [CI]: 0.69-2.54) or PFS (HR: 1.38, 95% CI: 0.74-2.55) between the groups. The overall response rate and complete response rate were 58% (95% CI: 43.2-71.8) and 32% (95% CI: 19.5-46.7) in all patients, and 55% (95% CI: 31.5-76.9) and 35% (95% CI: 15.4-59.2) in the cisplatin-unfit group, respectively. The common grade 3 of 4 adverse events experienced were neutropenia (78%), followed by thrombocytopenia (56%), anemia (46%), and febrile neutropenia (16%). The 24-hour urinary creatinine clearance did not differ significantly between the groups after one, two, or three courses of PCG. We found no significant difference regarding OS and PFS between the cisplatin-fit patients with a full dose of cisplatin and -unfit patients with cisplatin-dose-adjusted chemotherapy. In select cisplatin-unfit patients, PCG with dose adjustment of cisplatin may be useful for treating advanced/metastatic UC without any significant adverse events or impaired renal function compared with cisplatin-fit patients with a full dose of cisplatin.