Based on increasing evidence of the association between cancer-related inflammation and the progression of cancer, the external symptoms of systemic inflammatory response has been shown to be an indicator for the prognosis of many malignancies, including urological cancers. C-reactive protein, a representative acute-phase reactant, is a significant and sensitive inflammatory marker that can be objectively measured using reliable assays in clinical practice worldwide. C-reactive protein has been shown to be significant in the prediction of outcomes of urological cancers. The elevation of C-reactive protein levels, which indicate the presence of cancer-associated systemic inflammatory response, is linked to poorer survival in patients with urological cancers, including renal cell carcinoma, upper urinary tract and bladder cancers, and prostate cancer. With this strong prognostic ability, C-reactive protein can be incorporated into prognostic models and will make them simpler and improve their predictive accuracy. Furthermore, the longitudinal change of C-reactive protein level, C-reactive protein kinetics, provides additional information on patient survival outcomes. As such, C-reactive protein can be used to monitor treatment efficacy and disease course using serial measurements. In testicular cancer, C-reactive protein is associated with a risk of late complications, such as cardiovascular disease, and with the development of second non-germ-cell cancer. Taken together, these findings show that C-reactive protein can act as an important biomarker for urological cancers. This review discusses the importance of C-reactive protein as a prognostic biomarker in urological cancers on the basis of the currently available evidence.