Previous studies have shown that interleukin-17F (IL-17F) can markedly inhibit the angiogenesis of endothelial cells, implying that it may play a role in antiangiogenic therapy for tumors. To explore its effect on antiangiogenic therapy for hepatocellular carcinoma (HCC), we constructed a recombinant retrovirus vector RV-IL-17F expressing IL-17F, transfected SMMC-7721 human hepatocarcinoma cells with RV-IL-17F, and investigated the effect of transgene IL-17F expression on human hepatocarcinoma cells in vitro and in vivo in animal model. We demonstrated that IL-17F expression exerted no direct effect on in vitro proliferation and cell cycle of SMMC-7721 hepatocarcinoma cells, while it downregulated IL-6, IL-8, and VEGF expression in SMMC-7721 cells at both protein and mRNA levels and IL-17F-expressing supernatant from SMMC-7721/RV-IL-17F directly inhibited ECV304 vascular endothelial cell growth. Moreover, SMMC-7721/RV-IL-17F exhibited a significant decrease in tumor size and microvessel density as compared to the SMMC-7721/RV control when transplanted in nude mice. This retarded tumor growth in vivo elicited by IL-17F was associated with direct suppression of vascular endothelial cells and reduced expression of proangiogenic factors IL-6, IL-8, and VEGF leading to the inhibition of tumor angiogenesis. Thus, our results indicate that IL-17F, a novel antiangiogenic factor, may be useful in antiangiogenic therapy for HCC.