Background and Objectives: Dentin grafts have osteoinductive and osteoconductive properties and are considered as an alternative to autogenous graft. This study evaluates the efficacy of autogenous mineralized dentin graft (AMDG) alone or with xenograft and compares it with those of various graft materials used in the treatment of intraosseous bone defects. Materials and Methods: The third incisor teeth of six sheep (2–3 years old) were extracted and AMDG was obtained. Six defects were prepared on each tibia of these six sheep: empty defect (group E); autogenous graft (group A), dentin graft (group D), xenograft (group X), autogenous + xenograft (group A + X) and dentin + xenograft (group D + X). Three sheep in each group were sacrificed in the post-operative 3rd and 6th week and the histologic analyses were performed. Results: The D and D + X groups showed histological features similar to the other groups in the 3rd and 6th weeks. No statistically significant difference was found regarding the rates of new bone formation between the D and D + X groups (p = 1.0) and the other groups at both time intervals (p > 0.05). Conclusions: Similar results observed in this study between groups A, D, X, A + X and D + X demonstrate that AMDG can be successfully used in the treatment of intraosseous bone defects. Further experimental and clinical studies are needed to be able to evaluate the effectiveness of dentin grafts in different types of indications.