In order to evaluate the predictive effect of the controlled nutritional status (CONUT) score on the prognosis of patients with renal cell carcinoma (RCC) and upper urinary tract urothelial carcinoma (UTUC), a meta-analysis was performed. This systematic review has been registered on PROSPERO, the registration ID is CRD42021251879. A systematic search of the published literature using PubMed, Web of Science, Cochrane Library, EMBASE, and MEDLINE was performed. The fields of `renal cell cancer,` `upper tract urothelial cancer,` and `controlling nutritional status` and other fields were used as search terms. STATA 16 software was used to carry out data merging and statistical analysis of binary variables, Q test and χ(2) tests were used to verify the heterogeneity between the included works of studies. Subgroup analysis and sensitivity analysis were used to explain the sources of heterogeneity between studies. Begg's test was used to assess publication bias between studies. From the first 542 studies retrieved, through strict inclusion and exclusion criteria, 7 studies finally met the requirements and were included in the meta-analysis. Pooled results indicated that high CONUT indicates worse over survival (OS) [HR = 1.70, 95% CI (1.43-2.03), P = 0.02], cancer-specific survival (CSS) [HR = 1.84, 95% CI (1.52-2.23), P = 0.01], recurrence-free survival (RFS) [HR = 1.60, 95% CI (1.26-2.03), P = 0.116], and disease-free survival (DFS) [HR = 1.47, 95% CI (1.20-1.81), P = 0.03]. Based on cancer type, cutoff value, region, and sample size, a subgroup analysis was performed. The results showed that OS and CSS were not affected by the above factors, and the high CONUT score before surgery predicted worse OS and CSS. In conclusion, this meta-analysis revealed that the preoperative CONUT score is a potential independent predictor of the postoperative prognosis of RCC/UTUC patients. A high CONUT predicts worse OS/CSS/DFS and RFS in patients.