Fibroblast growth factors (FGFs) are important intercellular signaling molecules in developmental processes. Here, we show that FGF10 is secreted by cultured preadipocytes and that prevention of FGF10 signaling inhibits the expression of C/EBPβ and the subsequent differentiation of these cells. An active form of C/EBPβ rescued differentiation of the cells in which FGF10 signaling was blocked. Development of white adipose tissue and the expression of C/EBPβ in this tissue of FGF10 knockout mice were markedly reduced, and the ability of embryonic fibroblasts derived from FGF10 knockout mice to differentiate into adipocytes was impaired. Therefore, FGF10 plays an important role in adipogenesis, at least partly by contributing to the expression of C/EBPβ through an autocrine/paracrine mechanism.