In metastatic pancreatic adenocarcinoma, a high neutrophil-to-lymphocyte ratio (NLR) at diagnosis is a marker of poor prognosis. The prognostic role of baseline NLR and NLR change during first-line chemotherapy were determined. We conducted a retrospective study by using data from a single-center prospective cohort and a randomized open-label, multicenter, randomized trial. Two hundred and twelve patients were analyzed. Baseline NLR>5 was an independent marker of poor prognosis for overall survival (HR=2.01, 95% CI 1.33-3.05; P=0.001) and progression-free survival (PFS; HR=1.80, 95% CI 1.23-2.65; P=0.0026). According to NLR dynamics (n=172), patients with NLR≤5 on days 1 and 15 had a significantly better prognosis than those with NLR≤5 on day 1 and NLR>5 on day 15 (HR=2.23, 95% CI 1.18-4.21; P=0.013), NLR >5 on day 1 and NLR ≤5 on day 15 (HR=3.25, 95% CI 1.86-5.68; P<0.001), and NLR>5 on days 1 and 15 (HR=3.37, 95% CI 1.93-5.90; P<0.001). Over time, bad responders (PFS <6 months) had significantly higher mean NLR than good responders (PFS>6 months; group effect: P<0.0001). Seven out of eight patients with baseline NLR>5 had circulating tumor DNA. This study confirmed the independent prognostic value of baseline NLR >5 in metastatic pancreatic cancer. The change in NLR early during chemotherapy was also a prognostic indicator in patients with NLR ≤5.