To develop a new prognostic model for the overall survival of patients with clear cell metastatic renal cell carcinoma (mRCC) using Korean Renal Cancer Study Group (KRoCS) database and compared it with 2 renowned prognostic models: the Memorial Sloan Kettering Cancer Center (MSKCC) and the international metastatic renal cell carcinoma database consortium (IMDC) models.Data of 790 patients diagnosed with mRCC and receiving targeted therapy as their first-line treatment were pooled to this study. Data from 4 hospitals (n = 619) were used to develop the new model and those from other 5 hospitals (n = 171) were used for external validation. After detecting prognostic factors in multivariable Cox proportional-hazards regression analysis, patients were classified into 3 risk groups, favorable (0), intermediate (1–2), and poor (3 and more) by the number of prognostic factors.Seven variables such as more than 2 metastasis sites, no prior nephrectomy, Eastern Cooperative Oncology Group performance status ≥2, low hemoglobin, high serum corrected calcium, high neutrophil, high serum alkaline phosphatase were identified as prognostic factors for poor overall survival. Also, risk groups were categorized into 3 groups; median overall survival was 61.1 months in favorable, 26.5 months in intermediate, and 6.8 months in poor group. KRoCS ranked the first in all 3 statistical parameters including akaike information criterion (AIC), concordance index and generalized R2 among other prognostic models.We developed the KRoCS model and validated it externally with demonstrating its superiority over MSKCC and IMDC models. The KRoCS model can provide useful information for counseling patients with clear cell mRCC regarding life-expectancy.