Propofol, a common intravenous anesthetic, has been found to exert anti-cancer effects with inhibition of cancer cell proliferation, migration and invasion. We tested its possible action against HER2-overexpressing breast cancer cells that developed resistance against trastuzumab. Cell viability assay, ELISA for cytokines, mammosphere formation, quantitative RT-PCR for EMT/IL-6-targeting miRNAs and the in vivo experimental pulmonary metastasis model were performed to understand the epigenetic action of propofol. Propofol sensitized HER2 overexpressing cells to trastuzumab but such action was even more pronounced in resistant cells. Increased cytokines IL-6 as well as IL-8 were released by resistant cells, along with increased mammospheres and induction of EMT, all of which was inhibited by propofol. IL-6 targeting tumor suppressor miR-149-5p was found to be the novel miRNA that was up-regulated by propofol, resulting in the observed effects on cell viability, IL-6 production, mammospheres generation as well as EMT induction. Further, antagonizing miR-149-5p attenuated the propofol effects confirming the epigenetic activity of propofol through miR-149-5p regulation. Finally, in vivo validation in an experimental metastasis model conformed an inhibitory action of propofol against experimental lung metastasis and the essential mechanistic role of miR-149-5p/IL-6 loop. These results present a novel role of general anesthetic propofol against resistant breast cancer cells and the underlying epigenetic regulation of a tumor suppressor miRNA.