Aim: Methylcobalamin (MeCbl) is known to promote peripheral nerve regeneration and polarize macrophage to M2. In recent years, it has been reported that the regeneration of peripheral nerves and the polarization of macrophages to M2 are important for bone formation. The purpose of this research is to examine the effects of MeCbl on bone formation via peripheral nerves and macrophages. Methods: Effects of MeCbl were evaluated using rat skull defect models. Briefly, we created a bone hole in the rat skull, and evaluated the bone formation rate in the defect area in a group that received continuous administration of MeCbl and a group that received continuous administration of saline. In addition, MeCbl was administered to the culture medium for dorsal root ganglia (DRG) or macrophages to evaluate the expression of proteins and genes such as CGRP, BMP-2, and NGF, which involved in bone formation. Furthermore, DRG or macrophages treated with MeCbl were co-cultured with osteoblast and we evaluated the differentiation of the osteoblast. Results: In rat skull defect model, bone formation was significantly promoted in the MeCbl group at 4 and 8 weeks postoperatively. MeCbl significantly enhanced CGRP expression and release in DRG. In macrophages, MeCbl significantly increased the expression of genes such as BMP-2 and NGF. DRG or macrophages were co-cultured with osteoblast and MeCbl promoted osteoblast differentiation in both conditions. Conclusions: MeCbl promotes bone formation due to increasing the expression and release of CGRP in peripheral nerve and stimulating the expression of BMP-2 and NGF in macrophage.