Background: Baselinehigh neutrophil to lymphocyte ratio (NLR) has been associated with inferior overall survival in patients with stage III/IV NSCLC. Inflammation and neutrophilic infiltrates in the tumor microenvironment appear to inhibit anti-tumor immune response. We suspect that NLR might reflect the level of inflammation in tumor microenvironment. The objectives of this study were to evaluate potential relationships between pretreatment NLR and and PFS and OS in advanced NSCLC patients treated with second-line nivolumab or pembrolizumab. Methods: Patients with stage IV NSCLC who received at least one cycle of nivolumab or pembrolizumab after first-line treatment with a platinum doublet between January 2015 and December 2016 were included. Patient demographics including NLR at baseline, date of starting immunotherapy, and date of progression were recorded. The association between NLR and duration of response was assessed using a Mann-Whitney-Wilcoxon test. A cutoff of NLR of 3.5 and 5.0 based on published data (ref) were analyzed for differences in median overall survival and progression free survival. Results: 113 patients were analyzed: median age 68, male/female 38.9%/61.1%, 15% never smoked. The median PFS for patients with NLR < 5 was 4.14 months vs. 2.27 months in those with NLR > 5 (p = 0.031). Overall survival was also impacted by NLR. There were a total of 29 deaths in the cohort, 24 of these occurred in patients with NLR > 3.5 and 5 were in patients with NLR < 3.5. A lower NLR at baseline was significantly associated with improved overall survival (p = 0.036). Conclusions: A low baseline NLR is associated with superior progression free survival and overall survival in metastatic non-small cell lung cancer patients treated with nivolumab or pembrolizumab. These findings suggest that evaluating mediators of inflammation might help to identify potential therapeutic targets which could enhance effectiveness of PD-1 immune check point inhibitors in advanced NSCLC.