INTRODUCTION: Bone defect above critical size does not heal completely by itself and thus represents major clinical challenge to reconstructive surgery. Tissue engineering is a new approach for the repair of osseous defects. β tricalcium phosphate (β-TCP) loaded with autogenous bone marrow derived mesenchymal stem cells (BMSCs) is suggested to have a promising osteogenic characteristics that support its potential in tissue engineering to repair bone defects. OBJECTIVES: was to evaluate the efficacy of autogenous (BMSCs) by its transplantation into local defects using (β-TCP) as a carrier. MATERIALS AND METHODS: Ten male Mongrel dogs weighing 25 Kg were used in this study. Right and critical size bone defects (CSDs) were performed intraorally at the mandibular premolar area by the aid of trephine bur, of 6mm outer diameter and 5mm inner diameter. Right side bone defects (Experimental) were filled with mixture of (β-TCP) and (BMSCs) which was taken from bone marrow aspirate concentrates (BMACs) from the same animal. Meanwhile, the left side bone defects (control) were left empty for healing spontaneously. The effect of (BMSCs) was assessed histologically as well as histomorphometrically after 6 weeks. RESULTS Greater amount of bone formation was noticed in (CSDs) filled with (β-TCP) and (BMSCs). The amounts of new bone formed in the defects filled with (β-TCP) and (BMSCs) were significantly greater than those formed within the defects that were left empty. CONCLUSIONS: Autogenous (BMSCs) has excellent osteogenic characteristics and can be added to bone grafts following surgical and periodontal surgeries to enhance bone regenerative capacity.