Objective: To investigate the utilization of alginate carrier for delivering osteoblasts and creating new bone tissue in nude mice via injection. Methods: Bone marrow cells harvested from the iliac bone of New Zealand rabbits were cultured and induced to form osteoblasts. The osteoblasts were mixed with 2.0% alginate sodium solution to generate osteoblasts/alginate composites with a final cellular density of 5 x 10⁶/mL. Calcium chloride was used as a cross-linking agent to the gel aqueous alginate solution. The osteoblasts/alginate composites were injected into the dorsal subcutaneous tissue of nude mice. Results: Four and 8 weeks after injection, the hard knobbles were easily palpated under the dorsal skin. X-rays showed that the knobbles had calcified and had more density than the surrounding soft tissue. In histological analysis, new bone formation was observed in the osteoblasts/alginate composites. The osteogenesis was in association with regenerated hematopoietic bone marrow. Conclusion: These results reveal that new bone tissue could be created through the injection of alginate sodium mixed with marrow stromal osteoblasts.