To be specific, we confirmed that PIM1 could phosphorylate RUNX3 to promote its translocation from nucleus to cytoplasm; PIM1 inhibition, either by knocking down PIM1 or kinase inhibitor, could attenuate the BrCSC‐like traits of breast cancer cells; RUNX3 were confirmed to mediate the anti‐BrCSC effects of PIM1 inhibition. The gene discussed is PIM1; the disease is breast cancer.