Introduction: Mandibular fractures are considered the most common facial bones fractures. Treating mandibular fractures is difficult due to probability of complications, and there is presently no consensus on the best therapy. Aim: This study aimed to evaluate the role of xeno-hydroxyapetite bone graft in the healing of unfavorable oblique mandibular fractures under rigid fixation. Material and methods: This experimental study included 18 healthy male dogs. Unilateral mandibular fractures were induced for all animals. Animals were divided equally into: Control group (I) where the fracture was fixed with reconstruction bone plate only. Study group (II) where the fracture was fixed with reconstruction bone plate and bone defect was filled with the xeno-hydroxyapetite bone graft. The bone defect site was examined radiographically, Histopathologically and histomorphometrically at 2, 4 and 8 weeks. Results: There was significant increase in bone density with increasing time in both groups. The analysis of histological sections revealed that the newly formed bony spicules in both groups were localized randomly and in discrete puncta within the graft material. Histomorphometry analysis suggests that the bovine bone graft showed well-organized and reconstructed bone similar to native bone tissues. Conclusion: Xeno-hydroxyapetite bone graft is a good choice for the jaw bone reconstruction and can reduce the healing time in the area of the fracture line. Xeno-hydroxyapetite bone graft can be satisfactorily used as grafts in the treatment of unfavorable mandibular fractures.