Vital pulp therapy is the method for the treatment of reversible pulpitis. The ultimate goal of vital pulp therapy is to rapidly regenerate dentin of excellent quality by using an external agent that possesses novel properties such as biocompatibility and bioactivity.Dentin phosphophoryn (DPP) is the most abundant of the non-collagenous polyanionic phospho proteins in dentin. The purpose of this study was to examine the effects of DPP on differentiation and mineralization of odontoblasts. MDPC-23, a rat odontoblast-like cell line was used in this study in vitro and to investigate mineralized-matrix induction ability of DPP in vivo. The cells were cultured with DPP at different concentrations (0, 0.1, 1, and 10 µg/mL). The cell-morphology and proliferation were evaluated. Furthermore, cells were analyzed for mRNA expression of dentin/bone-related proteins by RT-PCR. Moreover, ALPase activity and Alizarin red staining were performed for confirmation of mineralization induced by DPP. The addition of DPP did not affect on proliferation or morphology of MDPC-23. The mRNA expressions of DMP-1 and ALPase were promoted by 0.1, 1 and 10 µg/mL of DPP. Moreover, the mRNA expressions of Osteorix, BSP and OCN were promoted by 1 and 10 µg/mL of DPP but Runx2 and OPN expressions were prominent in case of 10 µg/mL of DPP. The high ALPase activity in MDPC-23 was induced by 1 and 10 µg/mL of DPP. The number of mineralized nodules was higher by addition of 1 and 10 µg/mL of DPP at 7 days. Mineralized-matrix induction was observed after 14 days of implantation of DPP-collagen and RPCs composites on the dorsal side of rat in vivo.This study showed that DPP promotes the differentiation and mineralization of odontoblasts in vitro and induction of mineralization in vivo. Therefore DPP can be a promising candidate for formulating a new pulp capping material.