Prader-Willi syndrome (PWS) is a rare neurodevelopmental disease caused by abnormality of chromosome 15q11-13. The estimated prevalence of PWS is 1/10,000-30,000. Most common features of this disease are feeding problems characterized by poor sucking habit related with neonatal or infantile hypotonia and obesity due to early childhood hyperphagia involved with lack of satiety. In the orodental findings, enamel hypoplasia, rampant caries, delayed eruption, poor oral hygiene, hypodontia, supernumerary teeth, increased tooth wear, decreased salivary flow and change in saliva composition were reported. This case report describes the dental treatment of 3-year-9-months-old male patient with PWS. Periodic check-ups and conservative treatments were followed, however, rapid dental caries progression caused by estimating hyposalivation was observed. Because of lack of patient cooperation, dental procedures were performed under general anesthesia.