Background: Chemotherapy-induced neutropenia (CIN) has been reported to be associated with a longer survival in patients with various cancers. The aim of our study was to assess whether CIN could also be a prognostic factor in patients with unresectable pancreatic cancer receiving treatment with gemcitabine (GEM) and nab-paclitaxel (nab-PTX). Methods: We retrospectively analyzed the medical records of pancreatic cancer patients who had been treated with GEM and nab-PTX as first-line chemotherapy. CIN was categorized on the basis of the worst WHO grade during chemotherapy: absent/mild (≦ grade 2), or severe (≧ grade 3). The background characteristics and CIN as time-varying covariates (TVCs) were analyzed as potential prognostic factors using a Cox proportional hazards model. Results: We analyzed a total of 291 patients (absent/mild CIN: 116 patients; severe CIN: 174 patients). The median time to severe CIN was 14 days (interquartile range: 10–39 days). The median overall survival (OS) was significantly longer in the severe CIN group than in the absent/mild CIN group (19.2 vs. 11.3 months; p < 0.001) After adjustments, severe CIN was identified as an independent predictor of the OS (HR, 0.54; 95% CI, 0.38–0.77; p = 0.001). In the TVC model also, severe CIN was identified as an independent factor (HR, 0.79; 95% CI, 0.68–0.92; p = 0.002). Conclusions: Severe CIN was associated with a longer survival in patients with pancreatic cancer treated with GEM and nab-PTX.