The study aimed to examine the impact of platelet rich plasma (PRP) on the healing of a mandibular bone defect in obese rats. In this research, forty-eight adult male albino rats were divided into two equal groups; Group 1: were fed on standard diet. Group 2: were fed on high fat diet for four weeks for obesity inducing. A bone defect on the right side of mandible was created in each rat then all rats were subdivided into two equal subgroups. In subgroups 1.1 and 2.1, the bone defects were left without treating whereas in subgroups 1.2 and 2.2 the bone defects were filled with PRP. Two and four weeks postoperatively, six rats per group were euthanized and the samples were processed histological examination, X-ray elemental microanalysis and scanning electron microscopic examination. The results showed that rats received high fat diet and their bone defects left untreated revealed delayed bone healing and depicted significant decrease in bone calcium level in comparison with other subgroups. Interestingly, rats received high fat diet and their bone defects filled with platelet rich plasma revealed marked progress in bone healing and exhibited significant increase in bone calcium level in comparison with rats received high fat diet and with untreated bone defect. Conclusion: Obesity impaired the healing of mandibular bone defect. However, PRP has the ability to offset the negative effect of obesity and promote bone healing in obese rats. Therefore, it is highly recommended in obese individuals to fill the surgical bone defects with PRP.