PURPOSE: Iron deficiency anemia (IDA) and sleep problems are prevalent in infancy and early childhood and are more associated with poor cognitive, motor, and social-emotional development. The aim of this study was to access the relationship between IDA and sleep disorders in a population of Korean children <36 months. METHODS: One hundred and ninety six children, who visited the outpatient clinic for a routine check-up were consecutively enrolled from March 2011 to March 2012. All parents answered a questionnaire about sleep patterns of their children using a modified expanded version of the Brief Infant Sleep Questionnaire. Among the subjects, 93 children with strong evidence of sleep disordered breathing were excluded. Hundred three children were then divided into the IDA group (n=23) and the control group (n=80). Sleep-wake parameters and prevalence of sleep disturbances were compared between the two groups. A multivariate analysis was performed to determine the independent risk factors for sleep disturbances in children. RESULTS: Children with IDA had more frequent nocturnal waking, restless sleep, and inconsolable crying during sleep than those in the control. Children with IDA also had more inappropriate sleep onset associations. No difference in sleep-wake parameters was observed between the two groups. The presence of IDA in children and maternal anemia were significant independent risk factors for sleep disturbances in children <36 months. CONCLUSION: The results suggest that prevention, early detection, and treatment of IDA would be important for good sleep in young children <36 months.