Simple Summary: Accurately predicting the recurrence of non-metastatic renal cell carcinoma following surgery is of utmost importance to guide follow-up recommendations, as well as adjuvant treatment indications. In this study, we looked at the prognostic role of the pre-operative neutrophil-to-lymphocyte ratio (NLR) in this setting. We found that the pre-operative NLR was an interesting bio-marker to predict disease recurrence and death. It is all the more interesting because it is inexpensive and easy to implement. Furthermore, it could increase the performance of the UISS classification (which is actually recommended to predict the risk of recurrence after nephrectomy) and allow to individualize a group of patients at very low risk who could benefit from a lightened follow-up. Recent studies suggested that the neutrophil-to-lymphocyte ratio (NLR) could play a key role in tumor initiation, progression and response to treatments. The main objective was to assess the prognostic value of the pre-operative NLR on recurrence-free survival (RFS) in patients with non-hereditary localized renal cell carcinoma. From the UroCCR database (NCT03293563), factors influencing the disease recurrence of consecutive patients who underwent nephrectomy for cT1-T4 N0M0 were analyzed using multi-variate cox regression and log-rank methods. We included 786 patients, among which 135 (17.2%) experienced a recurrence at a median time of 23.7 [8.5–48.6] months. RFS for patients with a pre-operative NLR of <2.7 was 94% and 88% at 3 and 5 years, respectively, versus 76% and 63% for patients with a NLR of ≥2.7 (p < 0.001, log-rank test). To predict the risk of post-operative recurrence, the NLR was combined with the UCLA integrated staging system (UISS), and we defined four groups of the UroCCR-61 predictive model. The RFS rates at 3 and 5 years were 100% and 97% in the very-low-risk group, 93% and 86% in the low-risk group, 78% and 68% in the intermediate-risk group and 63% and 46% in the high-risk group (p < 0.0001). The pre-operative NLR seems to be an inexpensive and easily accessible prognostic bio-marker for non-metastatic RCCs. [ABSTRACT FROM AUTHOR]