INTRODUCTION: Low-level laser therapy (LLLT) has been studied in many fields of dentistry due to its reparative and anti-inflammatory effect. Regarding the orthodontic tooth movement, LLLT accelerates tooth movement, reduces the pain, enhances bone remodeling and reduces the orthodontic inflammatory induced root resorption (OIIRR). OBJECTIVES: The aim of the present study was to assess histologically and histomorphometrically the effect of LLLT on OIIRR under heavy orthodontic force magnitude (50 g) in rat model. MATERIALS AND METHODS: Sixteen male Albino rats weighing from (250-300 g) were randomly assigned to two equal groups (8 rats each). Control heavy-force group (CH): the maxillary right first molars were subjected to orthodontic force of 50 g by placement of a coil spring. Laser high-force group (LH): the maxillary right first molars were subjected to orthodontic force of 50 g + LLLT at four points (two buccal and two palatal), 12 seconds per point, with a GaAlAs diode laser source irradiated with the dose of 4.8 J/cm2 (100 mW, 12 s, 0.6 J) on every other day during force application. The rats were sacrificed after 21 days of orthodontic force application. After sacrificing the rats; the maxillae were hemisected and serial sections of the area of maxillary right first molar were obtained and evaluated histologically and histomorphometrically. RESULTS: Root resorption was significantly decreased (p=0.001) in laser group (L) in comparison to the control group (C). In contrast, root resorption was the largest and deepest up to the dentin in the control group. Moreover, odontoclasts were observed especially in the C group indicating still active root resorption activities. In addition, increased blood vasculature and formation of reparative cementum layer covering the resorption lacunae were observed in the Laser group. CONCLUSIONS: LLLT seems promising in preventing or reducing orthodontic root resorption, in addition to accelerating and enhancing the healing and repair of OIIRR.