The aim of this study was to evaluate histologically the bone defect's regeneration after application of beta-tricalcium phosphate nanoparticles in diabetic rats. The experimental part was carried out on 16 adult male albino rats and their weight almost 250 gm., the animals were grouped into 2 equal groups as the following; group I (control diabetic) which had not receive the graft, group II (experimental diabetic) which had received the graft material (Nβ-TCP). Specimens were harvested on days 7 and 28 after surgical procedures, prepared and examined histologically by H&E stain, there were wide histological differences between the groups of this study along the different intervals of the study. The histological results demonstrated that there was obvious retardation in granulation tissue formation, organization and bone formation in the control diabetic group I than the other group along the different intervals of this study. This retardation in the healing of diabetic control group was due to the effect of diabetes as it reduces cellular proliferation in early callus, reduces collagen synthesis content, reduces osteoblastic activity and reduces bone mineralization. Moreover, there was great acceleration in granulation tissue formation, organization and bone formation in experimental diabetic group II which received the graft material. This enhancement in bone healing process was due to the stimulatory effect of Nβ-TCP on osteoblastic differentiation and enhanced functions of osteoblasts on nanophase ceramics.