MiR-375 is a tumor suppressor miRNA that is downregulated in hepatocellular carcinoma (HCC). However, due to the lack of effective delivery strategies, miR-375 replacement as a therapy for HCC has not been investigated. In the present study, we have developed a straightforward strategy to deliver miR-375 into HCC cells by assembling miR-375 mimics on the surface of AuNPs and forming AuNP-miR-375 nanoparticles. AuNP-miR-375 exhibits high cellular uptake and preserves miR-375's activities to suppress cellular proliferation, migration/invasion, and colony formation, and to induce apoptosis in HCC cells. Furthermore, AuNP-delivered miR-375 efficiently downregulated its target genes through RNA interference. In primary and xenograft tumor mouse models, AuNP-miR-375 showed high tumor uptake, therapeutic efficacy, and no apparent toxicity to the host mice. In conclusion, our findings indicate that AuNPs is a reliable strategy to deliver miR-375 into HCC cells and tissue, and that AuNP-miR-375 has the potential in the clinic for treatment of unresectable HCC.