Bone mass and strength is mediated by appropriate weight bearing, and it is clear that bone tissue senses and adopts mechanical stresses. However, the precise molecular mechanisms in mechanotransduction remain elusive. Recently, several studies clarified that estrogen receptor alpha (ERalpha) plays important role in mechanotransduction. For example, the lifespan of osteocytes is prolonged by mechanical loading through ERalpha action, which is produced by the plentiful expression of ERalpha in osteocytes. Although these recent findings clearly show the important role of ERalpha in mechanotransduction, the intracellular function of ERalpha is still largely unknown. In this point of view, it will be a great interest to elucidate how ERs functionally associate with regulators involved with mechanotransductions in bone cells.