The aim of this study was the evaluation of the discomfort level during the utilization of non oclusal intraoral appliance during sleep in patients with muscular temporomandibular dysfunction; time of acceptance; and the effectiveness of non oclusal intraoral appliance related to the relief of pain symptoms. We evaluated 30 patients from Orofacial Pain and Temporomandibular Dysfunction Clinic (UNIFESP/EPM/HSP) with muscular temporamandibular dysfunction, 25 females and 5 males, between 19 to 60 years. We used a non-oclusal intraoral appliance, based on the model developed by Minagi et al. (2001). Patients was conducted to use the appliance during all sleeping period e to persist in use, even when there was any kind of discomfort, which would be natural during the adaptation period, for 30 consecutive days. After this period, the researcher interviewed all patients, answering specific questions designed for this study. The mean time for adaptation was 4 days. Of all patients, 23.33% had no difficulty in adapting the appliance, with immediate acceptance. The gradual reduction in the intensity of myofascial pain and discomfort, as well as improving the quality of life in 78.3% of the sample confirmed the effectiveness of non-oclusal palatal intraoral appliance without occlusal contact in relieving the painful symptoms of muscular TMD.