Objectives: Metastatic breast cancer is an advanced stage that is highly dependent on migration signaling pathways, though it remains unclear what mechanisms control the maintenance of tumorigenic cells that drives the migration and invasion processes. This in vitro study examined the intercellular cross-talk in MCF-7 and MDA-MB-231 breast cancer cells when treated with the simultaneous administration of docetaxel (DOC) and thymoquinone (TQ) loaded in nanoemulsion (NE) delivery system. Method: The cell cycle and breast cancer stem cells (BCSC) population were evaluated using flow cytometric analysis, alongside a DNA fragmentation assessment. Further molecular investigations were performed utilizing quantitative polymerase chain reaction (Q-PCR) technique. Results: The DOC+TQ/NE formulation inhibits the proliferation of human cancer cells by the G 2 /M phase and S-phase cell cycle arrest in MCF-7 and MDA-MB-231 cells, receptively, and it stimulates apoptosis through induction of DNA damage. Moreover, the DOC+TQ/NE causes a significant reduction in the cellular migration activity in both cell lines as detected by the wound-healing assay. This observation could possibly be mediated through the inhibition of BCSC, accompanied by marked down-regulation of SNAIL-1 and TWIST-1 expression. Conclusion: Overall, the results demonstrate that the co-delivery of DOC and TQ within NE formulation might be considered as a promising and effective therapeutic approach for breast cancer that could prevent the intercellular signaling function of metastasis.