Abstract The overall response rate for anti–PD-1 therapy remains modest in hepatocellular carcinoma (HCC). We found that a combination of IFNα and anti–PD-1–based immunotherapy resulted in enhanced antitumor activity in patients with unresectable HCC. In both immunocompetent orthotopic and spontaneous HCC models, IFNα therapy synergized with anti–PD-1 and the combination treatment led to significant enrichment of cytotoxic CD27+CD8+ T cells. Mechanistically, IFNα suppressed HIF1α signaling by inhibiting FosB transcription in HCC cells, resulting in reduced glucose consumption capacity and consequentially establishing a high-glucose microenvironment that fostered transcription of the T-cell costimulatory molecule Cd27 via mTOR–FOXM1 signaling in infiltrating CD8+ T cells. Together, these data reveal that IFNα reprograms glucose metabolism within the HCC tumor microenvironment, thereby liberating T-cell cytotoxic capacities and potentiating the PD-1 blockade–induced immune response. Our findings suggest that IFNα and anti–PD-1 cotreatment is an effective novel combination strategy for patients with HCC. Significance: Our study supports a role of tumor glucose metabolism in IFNα-mediated antitumor immunity in HCC, and tumor-infiltrating CD27+CD8+ T cells may be a promising biomarker for stratifying patients for anti–PD-1 therapy. See related commentary by Kao et al., p. 1615. This article is highlighted in the In This Issue feature, p. 1599