The purpose of this study was to evaluate the effect of photombiomodulation (PBM) and locally applied simvastatin on bone formation in critical size defects of the experimental rat model calvarium. A total of 28 Spraque-Dawley male rats, mean age of 18 weeks, were used. Bilateral 5 mm critical sized calvarial defects were created. Then 0.5 mg/mL simvastatin solution was inoculated into gelatin sponge and locally applied on one side. The other side served as control. Half of the animals were subjected to PBM treatment and the remaining half were left for spontaneous healing. The animals were sacrificed by guillotine at days 8 and 15. The specimens were histopathologically analysed. The histopathologic evaluation revealed that the new bone formation levels were significantly higher at the 15th day compared to the 8th day. The bone formation levels with PBM and simvastatin treatment either combined or applied individually were significantly higher than the control ones. PBM and local simvastatin applications had favourable effects on the early phase of new bone formation and reduced the bone healing period in the rat model. Further human trials must be performed for evaluation of the reliability of this protocol.