This study investigates the applicability of adipose mesenchymal stem cells (mADSCs) and hyaluronic acid (HA) as a cellular compound for bone tissue engineering. A critical bone defect was created on each femur of 25 rats in vivo, receiving the following 5 graft treatments: I-Control-defect; II-HA; III-mADSCs; IV-mADSCs+HA; and V-previously osteoinduced mADSCs+HA. Evaluation using microcomputed tomography, histomorphometry, and RT-PCR analysis was performed 23 days after implantation. Microcomputed tomography analysis indicated higher means of bone contact surface (BCS) and bone surface density (BSD) for the mADSCs+HA group compared with Control and the HA groups (P < 0.05). Histomorphometric findings showed higher means of bone regeneration in the mADSCs+HA compared with HA and Control groups (P < 0.05). The RT-PCR ratios showed no difference in type 1 collagen (Col1A) gene expression or osteopontin (OP) gene expression, whereas for the osteonectin gene (ON) higher means were found in the HA and mADSCs osteoin+HA groups (P < 0.05). These results suggest that a combination of HA and mADSCs without prior osteoinduction might be applicable for bone tissue regeneration.