Hepatocellular carcinoma (HCC) is a highly aggressive malignancy with a poor prognosis and high mortality. At present, vaccination with tumor cell lysate (TCL) loaded dendritic cells (DC) has been shown to be an effective therapy against HCC. However, the ability of promoting the specific T cell immune response is rather weak, influencing the antitumor response. Thus, it is necessary to find a strategy to improve the antitumor effect of TCL-loaded DC. Activation of signal transducer and activator of transcription 3 (STAT3) significantly inhibits antitumor immune response and DC maturity. Nifuroxazide, an antidiarrheal agent, has been proved to directly inhibit STAT3 activation. Thus, we investigated whether nifuroxazide could improve the antitumor immune response in mice vaccinated with TCL-loaded DC. The study provides the theoretical and experimental basis for developing an effective adjuvant for DC vaccine to treat HCC. Our results showed that the administration of nifuroxazide and DC-loaded TCL could significantly improve the survival rate, inhibit the tumor growth, and prompt the antitumor immune responses in mice with orthotopically implanted hepatocarcinomas, thus, possibly providing a new combination strategy to treat HCC.