Children with cerebral palsy (CP) suffer from several problems, so the family especially the mothers undertake a lot of social and emotional difficulties. The purpose of this study was to determine the severity of depression in mothers of children with CP in comparison with mothers who have normal children and its relation to the type of CP and severity of the disability. During this descriptive-analytic study, 43 mothers who had younger than 8 year-old children with CP under rehabilitation services in SABA clinic, related to the University of Social Welfare and Rehabilitation Sciences (USWR), Tehran, Iran, were selected as the case group by simple sampling. A data registration form and the Beck Depression Inventory II were completed by them. The type of CP and the severity of disability were determined by a pediatrician and an occupational therapist respectively, using the Gross Motor Function Classification System (GMFCS). Seventy-seven mothers of normal children, serving as the control group for comparing with case group, filled in the same questionnaires. There were significant differences in the mean depression scores (P=0.003) between the two groups. Having a child with CP also increases the risk of developing depression in mothers as much as 2.26 times (OR=2.26). There were no statistically significant differences in depression scores and the severity of disability and also among the five types of CP. It seems that having a child with CP is probably associated with higher prevalence and severity of depression in mothers. So treatment or prevention of depression in mothers of children with CP is highly recommended for improving the rehabilitation process and achieve better results in these children.