ABSTRACT Purpose This study aimed at validating the MBGR Orofacial Myofunctional Assessment Protocol (MBGR Protocol) for adults with Temporal Mandibular Disorders (TMD). Methods The study sample was composed of 30 adults: 15 with TMD (disc displacement with reduction according to the Research Diagnostic Criteria for Temporomandibular Disorders) and 15 control individuals. The validation process encompassed the content, criterion, and construct of the protocol, as well as its inter- and intra-rater agreement levels and sensitivity and specificity values, considering a 5% statistical significance level. Results The following validities were confirmed: of content, as the MBGR Protocol covers all functional issues present in patients with TMD; of criterion, with significant correlations between the MBGR and Orofacial Myofunctional Evaluation with Scores (OMES) protocols; of construct, differentiating individuals with and without Orofacial Myofunctional Disorders (OMD) as for pain on palpation and mandible range of motion, with significant correlation between the MBGR clinical evaluation and that using a digital algometer, as well as confirmation of the instrumental assessment for the breathing mode classification. Agreement ranged from poor to very good and from reasonable to very good for the inter- and intra-rater power analyses, respectively. High sensitivity and specificity values were observed. Conclusion The MBGR Protocol proved to be valid for use in adults presented with TMD with disc displacement with reduction and controls, covering all aspects that enable the analysis of OMD in these individuals.