α-Tocopherol is reported to activate the differentiation and fusion of osteoclast, however, it is not clear whether the excessive intake of vitamin E is a risk for osteoporosis. To investigate the effects of vitamin E and the dietary conditions on the osteoclastogenesis, osteoclast differentiation was evaluated using the bone marrow cells collected from mice fed various dietary conditions. Not only α-tocopherol but also γ-tocotrienol activated osteoclast differentiation in mice fed normal diet. Formation of large multinucleated cells was significantly increased by stimulation of nuclear factor-kappa B ligand (RANKL) in mice fed vitamin E deficient diet and was suppressed by the addition of α-tocopherol. Furthermore, there was no effect on bone density and no difference in osteoclast differentiation from the bone marrow cells collected from mice fed a high-fat diet with 0 or 1,000 mg/kg diet of α-tocopherol and tocotrienol, respectively. These results suggest that different type of diet affect the activation of osteoclast by α-tocopherol.