Background/Aim: Establishment of powerful and easy-to-evaluate biomarkers that can predict immune checkpoint inhibitor sensitivity in patients with gastric cancer (GC) would be highly useful. The albumin-derived neutrophilto-lymphocyte ratio (Alb-dNLR) score reportedly is an excellent measure of both immunity and nutritional status. However, the association between nivolumab treatment sensitivity and Alb-dNLR in GC has also not been adequately investigated. This multicenter retrospective study was designed to evaluate the association of Alb-dNLR with therapeutic sensitivity of nivolumab in GC patients. Patients and Methods: This was a retrospective multicenter study with patients from five sites. The data from 58 patients who received nivolumab for postoperative recurrent or unresectable advanced GC between October 2017 and December 2018 were analyzed. Blood tests had been performed before nivolumab administration. We analyzed the correlation between the Alb-dNLR score and clinicopathological factors, including best overall response. Results: Of the 58 patients, 21 (36.2%) comprised the disease control (DC) group and 37 (63.8%) comprised the progressive disease (PD) group. The nivolumab treatment responses were subjected to receiver operating characteristic analysis. The cutoff value was set to 2.90 g/dl for Alb and to 3.55 for dNLR. All eight patients in the high Alb-dNLR group had PD (p=0.0049). The low Alb-dNLR group had significantly better overall survival (p=0.0023) and progression-free survival rates (p<0.0001). Conclusion: The Alb-dNLR score was a very simple and sensitive predictor of nivolumab therapeutic sensitivity and has very good biomarker properties.Gastric cancer (GC) is the fifth most common cancer in the world, the third leading cause of cancer death, and has the highest incidence in East Asia (1). Systemic therapy can provide symptomatic relief, improved survival, and better quality of life in patients with locally advanced or metastatic GC. Although the prognosis of GC has gradually improved with better surgery, chemotherapy, and immune checkpoint inhibitors (ICIs), it is still not good enough.Regarding ICIs, the ATTRACTION-2 trial showed that nivolumab, an anti-programmed cell death protein 1 (PD-1) antibody, improved overall survival (OS) in GC patients who received at least two prior regimens of chemotherapy (2). Furthermore, the CheckMate 649 study revealed that nivolumab plus chemotherapy was recommended as first-line therapy for GC (3). Thus, the importance of ICIs in the treatment of GC has increased dramatically. However, the response rate to ICIs in GC patients is unsatisfactory, and the ATTRACTION-2 trial reported a response rate of 11.2% in 818