Family with sequence similarity three member C (FAM3C) (interleukin-like EMT inducer [11.11]), heat shock factor 1 (HSF1) and Ying-Yang 1 (YY1) have been independently reported to be involved in the pathogenesis of various cancers. However, whether they are coordinated to trigger the development of cancer remains unknown. This study determined the role and mechanism of YY1 and HSF1 in FAM3C-induced proliferation and migration of breast cancer cells. In human MDA-MB-231 breast cancer cell line, transforming growth factor-beta (TGF beta) up-regulated FAM3C, HSF1 and YY1 expressions. FAM3C overexpression promoted the proliferation and migration of MDA-MB-231 cells with YY1 and HSF1 up-regulation, whereas FAM3C silencing exerted the opposite effects. FAM3C inhibition repressed TGF beta-induced HSF1 activation, and proliferation and migration of breast cancer cells. YY1 was shown to directly activate HSF1 transcription to promote the proliferation and migration of breast cancer cells. YY1 silencing blunted FAM3C- and TGF beta-triggered activation of HSF1-AktCyclin D1 pathway, and proliferation and migration of breast cancer cells. Inhibition of HSF1 blocked TGF beta-, FAM3C- and YY1-induced proliferation and migration of breast cancer cells. YY1 and HSF1 had little effect on FAM3C expression. Similarly, inhibition of HSF1 also blunted FAM3C- and TGF beta-promoted proliferation and migration of human breast cancer BT-549 cells. In human breast cancer tissues, FAM3C, YY1 and HSF1 protein expressions were increased. In conclusion, FAM3C activated YY1-HSF1 signalling axis to promote the proliferation and migration of breast cancer cells. Furthermore, novel FAM3C-YY1-HSF1 pathway plays an important role in TGF beta-triggered proliferation and migration of human breast cancer MDA-MB-231 cells.