A synthetic analogue of resveratrol, 4-(6-hydroxy-2-naphtyl)-1,3-benzenediol (HS-1793), with improved photosensitivity and stability profiles, has been recently reported to exert anticancer activity on various cancer cells. However, the molecular mechanism of action and in vivo efficacy of HS-1793 in breast cancer cells have not been fully investigated. In the present study, we evaluated the effect of HS-1793 on hypoxia-inducible factor-1α (HIF-1α), which drives angiogenesis and the growth of solid tumors, in addition to the in vivo therapeutic effects of HS-1793 on breast cancer cells. HS-1793 was found to inhibit hypoxia (1.0% oxygen)-induced HIF-1α expression at the protein level, and its inhibitory effect was more potent than that of resveratrol in MCF-7 and MDA-MB-231 breast cancer cells. Furthermore, HS-1793 reduced the secretion and mRNA expression of vascular endothelial growth factor (VEGF), a key mediator of HIF-1-driven angiogenesis, without affecting cell viability. To evaluate the anticancer effects of HS-1793 in vivo, triple-negative MDA-MB-231 breast cancer xenografts were established in nude mice. HS-1793 significantly suppressed the growth of breast cancer tumor xenografts, without any apparent toxicity. Additionally, decreases in Ki-67, a proliferation index marker, and CD31, a biomarker of microvessel density, were observed in the tumor tissue. Expression of HIF-1 and VEGF was also downregulated in xenograft tumors treated with HS-1793. These in vivo results reinforce the improved anticancer activity of HS-1793 when compared with that of resveratrol. Overall, the present study suggests that the synthetic resveratrol analogue HS-1793 is a potent antitumor agent that inhibits tumor growth via the regulation of HIF-1, and demonstrates significant therapeutic potential for solid cancers.