Background: In several conditions we have face cranial bone defects. Reconstruction of these defects remains one of the most challenging problems encountered by craniofacial surgeons. Objective: To evaluate bone repair in cranial bone defects by use of an implant made of octacalcium phosphate in combination with bone matrix gelatin (OCP/BMG). Methods: We used 40, 5–6-week-old male Sprague-Dawley rats. A full thickness standardized trephine defect—5-mm in diameter—was made in the rat parietal bone and OCP/BMG was implanted into the defect. No OCP/BMG particles were implanted in control group that was otherwise treated identically. After sacrificing the rats chronologically and processing the tissues by routine histological procedures, 5-mm thick sections of bone were stained and examined under light microscope. Results: On the 5th day of implantation, inflammatory cells were seen around the implanted materials, especially around the OCP particles. By the end of 21st day, almost all of the OCP/BMG particles were absorbed and bone trabeculae, bone marrow cavities and bone marrow tissues were seen. In the control group, at the end of 21th day, a few areas of new bone were seen near to the defect margins and host bone, however, in much less amount than in the experimental group. Conclusion: Implant of OCP/BMG appears to stimulate new bone regeneration in bone defects. These biomaterials can be used for repair of cranial bone defects.