The purpose of this study was to estimate the prevalence of overweight and examine relationships between weight status of children with intellectual disabilities (IDs), mothers' perceived weight status of children, and socioeconomic status (SES). A cross-sectional study of 206 mothers of children with IDs in six special schools in Seoul, South Korea, was conducted. Data were collected through school health record abstraction and parent survey during December 2004. Relationships between measures were assessed using chi-square (chi[superscript 2]) with Fisher's exact test, analysis of variance (ANOVA), and logistic regression modeling while stratifying by mothers who overestimated versus underestimated their children's weight status. Almost half (46.6%) of the children were overweight, and 72.8% of mothers accurately perceived their children's weight status. Overweight among children with IDs in South Korea appears to be a more prevalent problem than expected. This study suggests the need for school-based weight management interventions for children with special needs. (Contains 4 tables.)