Dental follicle cells (DFCs) differentiate into cementoblasts or osteoblasts under appropriate triggering. However, the mechanism(s) for osteogenic differentiation of DFCs are still unclear. The purpose of this study was to examine the effects of dental papilla-derived human dental pulp cells (hDPCs) on osteogenic differentiation of human DFCs (hDFCs) in vitro and in vivo and to compare gene expression in hDFCs in the presence or absence of hDPCs. To evaluate the osteogenic differentiation of hDFCs induced by hDPCs, hDFCs were cultured in osteogenic medium with or without hDPCs-conditioned medium (CM) in vitro and the cells transplanted into the subcutaneous tissue of immunodeficient mice in vivo. The hDPCs-CM enhanced alkaline phosphatase promoter activity of hDFCs in osteogenic culture. The expression of several osteoblast marker genes was increased in hDFCs treated with hDPCs-CM compared to hDFCs in normal medium. The hDFCs induced by hDPCs-CM also produced more calcified nodules than hDFCs in normal medium. In transplantation experiments, hDPCs-CM promoted the osteogenic induction and bone formation of hDFCs. Microarray analysis and quantitative real-time PCR showed that osteogenesis-related genes including WNT2, VCAN, OSR2, FOSB, and POSTN in hDFCs were significantly upregulated after induction by hDPCs-CM compared to hDFCs in normal medium. These findings indicate that hDPCs could increase the expression of osteogenic genes in hDFCs and stimulate their osteogenesis and could be a cellular resource for bone regeneration therapy when induced by hDPCs-derived factors.