Background and Objective: Sleep behaviors have a significant impact on a childchr('39')s quality of life; thus, sleep disorders are a major concern for parents. These disorders show the highest prevalence amongst pre-school children which can lead to mood disorders and the disruption of cognitive and emotional abilities. These side effects can subsequently cause failure in school, family problems and psychiatric disorders. Material and Methods: Primarily, a list of kindergartens located in Zanjan city were selected with the help of the State Welfare Organization of Iran. The cluster sampling method was used and 345 samples were randomly entered to the study. Parents were asked to respond to the researcher’s questions based on BEARS questionnaire. Finally, the data were analyzed using SPSS software. Results: 304 out of 345 children participating in the study (88%) had sleep disorders. Fear of sleeping alone was the most reported sleep disorders (59.4%). Our study showed that the use of mass media reduced sleep-related problems (P=0.027). There was a significant relationship between maternal education and sleep disorders, and the lowest prevalence of sleep disorders was observed amongst children whose mothers held a bachelorchr('39')s degree (P=0.008). Conclusion: The high prevalence of sleep disorders in this study suggests that such psychological problems require special attention on the part of pediatricians, pediatric psychiatrists and general health professionals with an orientation towards teamwork. Keywords: Sleep Wake Disorders, Child Preschool, Iran