The baseline value of neutrophil to lymphocyte ratio (NLR) has been found to be prognostic in patients with metastatic castration resistant prostate cancer (CRPC). We evaluated the impact of baseline NLR and its change in patients receiving enzalutamide. We included consecutive metastatic CRPC patients treated with enzalutamide after docetaxel and studies the change of NLR (>3 vs ≤3) after week 4 and 12 weeks. Progression-free survival (PFS), overall survival (OS) and their 95% Confidence Intervals (95% CI) were estimated by the Kaplan-Meier method and compared with the log-rank test. The impact of NLR on PFS and OS was evaluated by Cox regression analyses and on prostate-specific antigen response rates (PSA RR; PSA decline >50%) were evaluated by binary logistic regression. Data collected on 193 patients from 9 centers were evaluated. Median age was 73.1 years (range, 42.8-90.7). The median baseline NLR was 3.2. The median PFS was 3.2 months (95% CI = 2.7-4.2) in patients with baseline NLR >3 and 7.4 months (95% CI = 5.5-9.7) in those with NLR ≤3, p < 0.0001. The median OS was 10.4 months (95% CI = 6.5-14.9) in patients with baseline NLR >3 and 16.9 months (95% CI = 11.2-20.9) in those with baseline NLR ≤3, p < 0.0001. In multivariate analysis, changes in NLR at 4 weeks were significant predictors of both PFS hazard ratio (HR) 1.24, 95% confidence interval (95% CI) 1.07-1.42, p = 0.003, and OS (HR 1.29, 95% CI 1.10-1.51, p = 0.001. A persistent NLR >3 during treatment with enzalutamide seems to have both prognostic and predictive value in CRPC patients.