Recently, the orofacial myofunctional therapy (OMT) has appeared as a possible alternative treatment for obstructive sleep apnea (OSA). Systematic reviews are required to achieve scientific evidence, seeking to direct the decision on therapeutic issues. The aim of this study was to systematically review the literature about the OMT proposals in adults with OSA related to symptoms and physiological parameters. Data sources were Lilacs, MEDLINE, Pubmed, Cochrane and Scielo using the descriptors: obstructive sleep apnea; myofunctional therapy; oropharyngeal exercises; breathing exercises; upper airway exercises; speech therapy. Studies published from 2000 to 2017 that evaluated the treatment with isolated OMT in subjects with OSA were included, obligatorily with polysomnographic data, pre and post therapy. Eight studies, out of 124 articles, were eligible according to the criteria adopted. Two systematic reviews, one clinical trial, three randomized clinical trials, and two case reports were included. Six studies showed a decrease in the Apnea and Hypopnea Index (AHI), five studies showed improvement in the minimum SpO2, decrease in the Epworth Sleepiness Scale (ESS) and in snoring. OMT proposals refer to a three-month program changing the parameters related to partial reduction of AHI, ESS index, snoring, and partial increase of SpO2. There are few randomized studies.