Osteoclasts are differentiated from hematopoietic stem cells and become multinucleated giant cells through cell-fusion by a number of regulators. Among such regulators, transcription factors play pivotal roles by reorganizing gene networks. Recently, epigenetic regulators like histone modifiers and chromatin remodelers have emerged to be prerequisite for gene regulations by transcriptional factors. However, little is known about epigenetic controls during osteoclastogenesis and osteoclastic maturation. To address this issue, we tried to identify novel epigenetic regulators for fine control of NFATc1 function through biochemical approaches. Here, we summarize the new epigenetic regulation mechanism and epigenetic regulator which are required for normal osteoclastogenesis.