Parenting is a key factor for the development of children with intellectual and developmental disabilities. Therefore, early intervention programs should target parenting behaviors to improve children's developmental outcomes. The present study analyzed the effect of parental behaviors and other family factors on the cognitive and linguistic development of children with an intellectual disability (ID). Participants (n = 87, aged between 20 and 47 months) were recruited from several Spanish Early Intervention Centers. The children's development was assessed with the Bayley Scales of Infant Development (BSID-III) on two occasions. Besides questionnaires including family factors, 10-min mother-child and father-child interactions during free play were auto-recorded at home. Intensive statistical modeling on the two measurement occasions was used to select relevant predictors as well as their interactions. Child cognitive development models, including predictors such as mother's responsiveness and affection and father's teaching, had a predictive capacity between 22 and 26%. The language development models, including the mother's responsiveness and father's teaching scores amongst other predictors, yielded adjusted-R[superscript 2]s between 26 and 28%. This study's findings evidence that parental behaviors during adult-child interaction affect the development of children with intellectual disabilities. The study also provides data that can be used to guide early intervention.