Histone acetyltransferase MOF is involved in active transcription regulation through histone H4K16 acetylation. MOF is downexpressed in a number of human tumors, but biological function of MOF in endometrial cancer has not been fully defined. The estrogen receptor alpha (ERalpha) is a transcription factor that regulates estrogen-stimulated cell proliferation in hormone-responsive tumors. However, ERalpha expression is decreased in grade III ECa samples and high expression of ERalpha is associated with long disease-free survival in ECa. The molecular mechanism for these observations is still unclear. Here we demonstrate knockdown of MOF promotes ECa cell growth and proliferation in vitro and in vivo. Clinical evidence indicates that expression MOF is decreased and positively correlated with that of ERalpha in ECa tissues. Furthermore, MOF physically interacts with ERalpha and modulates ERalpha stability in ECa cells. In addition, MOF modulates expression of a subset of endogenous genes regulated by ERalpha. Taken together, our results define MOF as a potential tumor suppressor in ECa participates in maintenance of ERalpha protein stability and regulation of ERalpha action.