Introduction: Biomarkers for predicting the outcome of ipilimumab plus nivolumab (Nivo-Ipi) treatment in cancer patients have not been identified. Herein, we investigated the prognostic significance of inflammatory and nutritional markers in patients with advanced non-small cell lung cancer (NSCLC) receiving Nivo-Ipi. Methods: Our study retrospectively analyzed 101 patients with advanced NSCLC who received Nivo-Ipi at a single institution. Inflammatory and nutritional indices were correlated with patient outcomes and included the neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), systemic immune-inflammation index (SII), prognostic nutritional index (PNI), advanced lung cancer inflammation index (ALI), and Glasgow prognostic score (GPS). Results: The NLR significantly correlated with the PLR, SII, PNI, ALI, and GPS. Regarding therapeutic efficacy, the NLR, SII, and PNI predicted a partial response, and all indices predicted progressive disease. In subgroup analyses, the SII, PNI, and ALI predicted the outcome of patients with adenocarcinoma, whereas only the PNI predicted the outcome of patients with non-adenocarcinoma. The PNI and SII were the most useful indices in patients with a programmed death ligand-1 expression level of <1% and ≥1%, respectively. Conclusion: The NLR, PLR, SII, PNI, ALI, and GPS were significantly associated with the outcome of Nivo-Ipi treatment in patients with NSCLC. The PNI was the most suitable marker regardless of histological type. The SII and PNI were the most promising markers for patients with and without PD-L1 expression, respectively.