Polycaprolactone-tricalcium phosphate (PCL-TCP), a new composite scaffold, has been shown to facilitate early revascularization and speed up bone regeneration process. The objective of this study was to evaluate the effect of PCL-TCP seeded with mesenchymal stem cells (MSCs) on healing of the vertical bone critical sized defect in dog's mandible. Bone marrow aspirate from dog humerous was cultured and the stemness of the cells was examined by differentiation staining methods and flow cytometric analysis. Third passage subculture cells (5 × 105 cells) were loaded on 20 × 10 × 10 mm3 and incubated for 48 h. The presence of MSCs in the pores was evaluated by scanning electron microscope. Bilateral mandibular premolar teeth were extracted in four dogs and the buccal and lingual bone plates were reduced to make a vertical defect. Cell-loaded scaffolds were fixed in right side and left side received pure PCL-TCP scaffolds as a control side defects. Histomorphometric analysis after 8 weeks of the scaffold implantation showed higher amount of lamellar bone in the test side (48.63%) than control side (17.27%) (p < 0.05).The results suggest that PCL-TCP may be an appropriate scaffold for loading MSCs in bone regeneration. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.