Hypotonia, particularly of the masticatory and oropharyngeal muscles, is 1 of the main characteristics of Down Syndrome (DS), resulting in impaired speech, chewing and swallowing. Moreover, the complete or partial obstruction of the airways during sleep may occur due to hypotonia of the tongue, leading to snoring and sleep disorders, such as obstructive apnea and sleep bruxism. OBJECTIVE:: Analyze salivary levels of dopamine and cortisol and muscle activity before and after treatment with low-level laser therapy administered to acupoints in children with DS. METHODS:: A randomized, controlled, clinical trial will be conducted. Individuals 4 to 17 years of age with a diagnosis of DS and possible sleep bruxism will be screened at the Integrated Health Clinic of Nove de Julho University. We will evaluate orofacial dysfunction (Nordic Orofacial Test - Screening questionnaire), Masseter muscle activity during sleep will be assessed by BiteStrip and the masticatory muscles will be evaluated by electromyography (BTS TMJOINT) head posture as well as salivary cortisol and dopamine. After the evaluations, the participants will be randomized into 2 groups: Grupo 1 - treatment with low-level laser therapy at a wavelength of 808 nm; Group 2 - sham treatment (simulated laser therapy). Treatment will be conducted twice per week for a total of 12 sessions. The data will be tabulated and treated using GraphPad Prism version 7.0. The Kolmogorov-Smirnov test will be used to determine the normality of the data. Variables that fit the Gaussian curve will be expressed as mean and standard deviation. The ANOVA 2-way will be used for comparisons between the groups, with the significance level set to 5% (P < .05).ClinicalTrials registration number: NCT04211870.