Background: There is little information available about prognostic markers of GC (gemcitabine, cisplatin) in patients with advanced biliary tract cancer (BTC). Neutrophil/lymphocyte ratio (NLR) in several cancers was might to be a prognostic factor associated with clinical outcomes, we examine NLR in patient with BTC underwent chemotherapy (GC). Methods: Retrospective chart review for consecutive patients who underwent GC for advanced BTC in our institute were performed. The patients who were enrolled in ongoing clinical trials were excluded. Gemcitabine and cisplatin were administered intravenously at doses of 1,000 or 25 mg/m2, on day one and eight, every three weeks. We divided these patients based on estimated NLR, and evaluated the clinicopathological factors and survival in the two groups (NLR ≥ 3 or < 3). Results: 57 patients from 2013 to 2017 were reviewed. 23 patients were in NLR ≥ 3 group and 34 patients were in NLR < 3 group. Patients characteristics were as follows; median age, 68 years old (range: 38-83) years: male 36 (63%); primary tumor lesion, intrahepatic bile duct 6 (10%)/extrahepatic bile duct 32 (56%)/gallbladder 18 (32%)/ampulla of vater 1 (2%); therapeutic purpose, palliative 50 (88%)/adjuvant 5 (8%)/neoadjuvant 2 (4%); PS, 0/1. Response rate of the patients who had measurable lesion according to RECIST v1.1 was 17% (8/46), and disease control rate was 70% (32/46). The progression-free survival rate between the two groups is not significantly different. Although, the median overall survival (OS) of NLR ≥ 3 group was 11.8 months, while OS of NLR < 3 group was 29.2 months. The overall survival rate in the NLR ≥ 3 group was significantly lower than that in the NLR < 3 group (P = 0.0339). Conclusions: Our study confirmed that high NLR is associated with worse OS and PFS, and suggested it may be a predictive marker for GC chemotherapy in patients with BTC.