BACKGROUND: describe structural and myofunctional aspects of the stomatognathic system for a case of Beckwith-Wiedmann syndrome with macroglossia that received speech therapy intervention. PROCEDURES: first, the patient clinical data was collected from hospital files. An initial interview was carried through with the mother. Then, the patient was submitted to a clinical myofunctional evaluation. Some additional complementary examinations were also held (otolaryngological assessment, videofluoroscopy examination and audiological evaluation). After six months of myofunctional therapy using passive techniques, the patient was revaluated. RESULTS: in the first myofunctional evaluation we noted lips and cheeks' flabbiness, absence of lip seal and tongue with reduced tension, right hemihypertrophy and significant anterior projection. Difficulties in mastication and swallowing of solid food were also observed. After six months of myofunctional therapy, an increase in lips and cheeks' muscle stiffness, tongue posteriorisation with superior muscular tension, and appropriate performance in mastication and swallowing of solid food were evidenced. CONCLUSION: a precocious speech-therapy intervention, based on myofunctional therapy techniques, showed good results in this case - Beckwith-Wiedmann syndrome with macroglossia.