The renal safety of cisplatin-based chemotherapy has not been investigated in patients with urothelial carcinoma of the upper urinary tract (UUT-UC) who retain a solitary kidney after nephroureterectomy. This study aimed to assess and compare the renal safety and efficacy of gemcitabine-cisplatin (GP) and gemcitabine-carboplatin (GC) in these patients. The medical records of patients diagnosed with urothelial carcinoma at the Sun Yat-Sen University Cancer Center between January 2005 and December 2015 were retrospectively reviewed. The creatinine clearance (CrCl) and estimated glomerular filtration rate (eGFR) were used to assess renal function and were calculated using different formulas. A total of 71 patients were enrolled in this study; 48 patients were on GP, and 23 were on GC. The renal function indicators (CrCl and eGFR) were all significantly lower after GP chemotherapy than at baseline, a phenomenon that was not observed in the GC group. Severe nephrotoxicities (SNTs) were reported in 12 patients on GP (25%) and zero on GC. SNT risk factors included a more than 20% decrease in eGFR after one GP cycle and the presence of diabetes (all p < 0.05). Among patients treated with first-line palliative chemotherapy (n = 32), GC (n = 13) patients had an ORR of 46.2%, which was not significantly different from GP patients (36.8%, n = 19), whereas GC patients tended to have a shorter OS than GP patients (9.2 vs. 29 months, p = 0.200). Our results confirm that GP has an adverse impact on the renal function of patients with UUT-UC who retain a solitary kidney, but it can be safely administered to the majority of these patients without inducing SNT. In specific patients, GC is an alternative to GP that has comparable efficacy and favourable renal toxicity.