Introduction: Bilateral sagittal split osteotomy (BSSO) is a technique commonly used to correct mandibular disproportions, while neurosensory disorders are common following this technique. Low-level laser irradiation has shown promising results to relieve the neurosensory disorders of BSSO technique. Objective:The aim of this study was to compare the effects of low-level laser irradiation on the neurosensory complications related to the BSSO technique. Materials and methods:In this prospective, double-blinded clinical trial, 13 patients candidate for BSSO surgery were selected and went under complete clinical neurosensory tests (CNTs) including brush stroke discrimination; two-point discrimination; and contact, thermal, and pinprick discrimination, as well as visual analog scale (VAS) assessments. The laser GaAlAs (820-830 µm wavelength) irradiation was done for total six sessions after surgery for the patients at one side accidentally, and the opposite site was a control by irradiation of placebo. The values of CNT assessments between the experimental and control sites were analyzed employing Wilcoxon signed-rank test.Results: Higher values of VAS and brush stroke discrimination test were observed in the laser-irradiated sites than in the control sites, although without any significant differences (p > 0.05). Moreover, significantly higher values of pinprick discrimination test were noted in the experimental sites on days 1, 2, 3, 4, 7, 14, 28, and 60 (p < 0.05). The thermal test results were higher in the study sides, and the differences of both sides were significant on days 2, 3, 4, 7, 14, and 28 (p < 0.05). Conclusion:In total, GaAlAs low-level laser irradiation after the BSSO surgery results in both subjective and objective improvements regarding the time and magnitude of return of function; however, in some tests no significant differences were found between laser-irradiated and control areas.