Pembrolizumab plus chemotherapy has been indicated as the first-line treatment for metastatic or unresectable locally advanced esophageal cancer. However, pretreatment biomarkers for predicting clinical outcomes remain unclear. We investigated the predictive value of inflammation-based prognostic scores in patients treated with pembrolizumab and chemotherapy. The Prognostic Nutritional Index (PNI), C-reactive protein/albumin ratio (CAR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) were calculated before initial treatment in 65 eligible patients with metastatic or unresectable locally advanced esophageal cancer receiving pembrolizumab plus CF therapy, and the relationship between these biomarkers and clinical outcomes was analyzed. The objective response rate (ORR) and progression disease (PD) were observed in 51% and 21% of all patients. Patients with PNI<39 have significantly worse treatment responses than those with PNI≥39 (ORR; 28% vs. 60%, PD; 44% vs. 13%, P =0.020). Progression-free survival (PFS) is significantly associated with the PNI and CAR ( P <0.001 and P =0.004, respectively). Overall survival (OS) is associated with PNI, CAR, and PLR ( P <0.001, P =0.008, and P =0.018, respectively). The PNI cutoff value of 39 is identified as an independent factor for PFS (odds ratio=0.27, 95% CI: 0.18-0.81, P =0.012) and OS (odds ratio=0.22, 95% CI: 0.08-0.59, P =0.003). Patients with PNI<39 have significantly worse 6-month PFS and 1-year OS than those with PNI≥39 (27.8% vs. 66.7%, 27.2% vs. 81.1%, respectively). In conclusion, inflammation-based prognostic scores are associated with survival in patients treated with pembrolizumab plus CF therapy. Pretreatment PNI is a promising candidate for predicting treatment response and survival.