Introduction: Unilateral hearing loss has devastating effects on sound localization, speech understanding in adverse listening conditions, academic achievement, behavior and learning of Hearing impaired children. Early detection and intervention with regard to the issues of unilateral hearing loss is important in young children. The main goal of this study was to determine the prevalence of unilateral hearing loss among kindergarteners aged 3-6 years in Hamadan city, 2012.Material and Methods: In this cross-sectional descriptive study, 345 subjects (185 female, 160 male) were selected through random sampling. Play Audiometry test was used to determine the hearing threshold.Results: The results indicated that from the sum of 690 ears, 30(4.3%), had unilateral hearing loss; 26 (3.8%) with conductive hearing loss, 3 (0.4%) with sensorineural hearing loss and one (0.1%) with mixed hearing loss. No significant differences were observed between paired ears, genders and different ages.Conclusion: In this study, the prevalence of unilateral hearing loss was high (4.3%), 3.8% is conductive hearing loss accruing least one during childs language learning. Given the high prevalence of unilateral hearing loss in children 3-6 years of age, and the importance of this period in speech, language and learning development, early diagnosis and intervention is essential.