For many malignancies, inflammation-based scores correlate with survival. The neutrophil-to-lymphocyte ratio (NLR) and prognostic nutritional index (PNI) are immunonutritional indices associated with postoperative outcomes in patients with hepatocellular carcinoma (HCC). We evaluated whether a combined preoperative NLR and PNI score was prognostically superior to either index alone in 793 patients with unresectable HCC after transarterial chemoembolization. Patient demographic, clinical, and pathological data were also collected and analysed. A receiver-operating characteristic (ROC) analysis was used to classify patients as follows: NLR-PNI 0 group (NLR ≤ 2.2 and PNI > 46), NLR-PNI 1 group (NLR > 2.2 or PNI ≤ 46) and NLR-PNI 2 group (NLR > 2.2 and PNI ≤ 46). Regarding 1-, 3-, and 5-year survival, the NLR-PNI score had superior discriminative abilities (i.e., higher area under the ROC curve), compared with either the NLR or PNI alone, and patients in the NLR-PNI 0, 1, and 2 groups had median survival times of 33 (95% confidence interval: 22.8-43.2), 14 (10.9-17.1), and 6 (9.9-14.1) months, respectively. In multivariate analyses, the Barcelona Clinic Liver Cancer, total bilirubin, vascular invasion, and NLR-PNI score adversely affected overall survival. In conclusion, the NLR-PNI score can improve the accuracy of prognoses for patients with unresectable HCC.