Prader-Willi syndrome (PWS) is a genetic disorder which occurs with a frequency about one in 10,000-30,000 live newborns. Both males and females, and all races are equally effected. The numerous symptoms of PWS include the following: delay development, hyperphagia and obesity, changes in the salivary composition and consistency, enamel erosion, severe tooth wear, etc. This article presents a case of 3-year-old boy with PWS. Due to his multiple caries and behavior problem, the dental treatment was finished under general anesthesia. PWS involved many aspects, the early diagnosis and treatment are essential to improve the general health and the quality of the life for these individuals.