Background <p>Resveratrol (Res), a plant-derived polyphenol, exerts synergistic effects when combined with various chemotherapeutic drugs, enhancing the antitumor activity of traditional chemotherapy. However, whether Res combined with cisplatin (CDDP) produces a synergistic inhibitory effect on osteosarcoma cell growth and its underlying mechanisms remain unclear.</p> Methods <p>We investigated the responses of U2-OS cells to Res, CDDP, or their combination using Cell Counting Kit-8 (CCK-8) for proliferation, flow cytometry for apoptosis, wound healing assays for migration, and Transwell assays for invasion. The effects of the two drugs on Wnt/β-catenin signaling were analyzed via quantitative real-time PCR (qRT-PCR) and western blotting. Additionally, the relationship between Cx43 and Wnt/Wnt/β-catenin signaling was explored by knocking down Cx43 using lentiviral infection.</p> Results <p>The combination of Res and CDDP exhibited greater cytotoxicity against osteosarcoma U2-OS cells than either drug alone, and this effect was synergistic as determined by the Chou-Talalay equation. Cx43 knockdown attenuated the strong antitumor effect of the Res + CDDP combination and restored Wnt/β-catenin signaling activity. Furthermore, the Res + CDDP combination generated more reactive oxygen species (ROS) than individual treatments, inducing ROS-dependent apoptosis, which was blocked by N-acetylcysteine (NAC).</p> Conclusions <p>Res combined with CDDP exerts a synergistic inhibitory effect on osteosarcoma by upregulating Cx43 and inducing ROS-dependent apoptosis. This study may provide a novel therapeutic strategy and potential clinical applications for osteosarcoma treatment.</p>