Background: Preoperative nutritional status is reportedly associated with postoperative outcomes in patients with hepatocellular carcinoma. This study aimed to investigate the significance of the controlling nutritional status (CONUT) score and the prognostic nutritional index (PNI) as predictors of postoperative outcomes. Methods: We retrospectively reviewed data from 331 patients who underwent hepatectomy for hepatocellular carcinoma between January 2007 and December 2015. Patients were divided into 2 groups based on their CONUT score and the PNI. We evaluated the effect of the CONUT score and PNI on perioperative outcomes. Multivariate analysis was performed to identify independent predictors of in-hospital mortality after hepatectomy. Results: The high CONUT group had a significantly higher incidence of 30-day mortality (p < 0.001), in-hospital mortality (p = 0.002), ascites (p = 0.006), liver failure (p = 0.02), sepsis (p = 0.01), and enteritis (p < 0.001). The low PNI group was also significantly associated with 30-day mortality (p < 0.001), in-hospital mortality (p = 0.003), liver failure (p < 0.001), sepsis (p = 0.02), enteritis (p = 0.02), and hospital stay (p = 0.01). In multivariate analyses, a high CONUT score was an independent predictor of in-hospital mortality after hepatectomy (hazard ratio [HR] 9.41, p = 0.038), but the PNI was not (HR 5.86, p = 0.08). Conclusions: Preoperative assessment of the CONUT score is helpful for evaluating patients’ nutritional status and mortality risk after liver surgery.