Background <p>Benzaldehyde (BA) is an aromatic aldehyde found in fruits that has been studied as a potential anticancer agent on the basis of its ability to inhibit transformation in mouse embryo cells and to suppress metastasis in mice.</p> Methods <p>We investigated the cytotoxic effects of BA on cancer cells, and probed its effects on intracellular signaling pathways. The anticancer effects of BA in vivo were studied by using a mouse orthotopic transplantation model of pancreatic cancer.</p> Results <p>BA inhibited the growth of osimertinib- or radiation-resistant cancer cells as well as the interaction between 14-3-3ζ and its client proteins. The interaction of 14-3-3ζ with the Ser²⁸-phosphorylated form of histone H3 (H3S28ph) was implicated in treatment resistance and the transcriptional regulation of genes related to epithelial-mesenchymal transition and stemness, including <i>E2F2</i>, <i>SRSF1</i>, and <i>ID1</i>. Treatment of mice with a BA derivative inhibited pancreatic tumor growth and lung metastasis, as well as suppressed a state of epithelial-mesenchymal plasticity (EMP) of tumor cells.</p> Conclusion <p>The interaction between 14-3-3ζ and H3S28ph plays a key role in EMP and treatment resistance in cancer. The ability of BA to inhibit this and other interactions of 14-3-3ζ offers the potential to overcome treatment resistance and to suppress metastasis.</p> <p></p>