This cross-sectional study examined the association between parenting behavior, the parent-child relationship, and externalizing child behavior in families of children with mild to borderline intellectual disabilities (MBID). The families of a child with MBID and accompanying externalizing behavior problems (n= 113) reported more positive discipline and physical punishment but less involvement, less positive parenting, less monitoring, a lower sense of parenting competence, less acceptance of the child, and less closeness to the child than the families of a child with MBID and no accompanying externalizing behavior problems (n= 71). The parent-child relationship was most strongly associated with externalizing child behavior, over and above parenting behaviors. In addition, the parent-child relationship was found to be associated with parenting behavior, over and above the child's externalizing behavior. Our results highlight the importance of both the parent-child relationship and parenting behavior in connection with the occurrence of externalizing behavior problems on the part of children with MBID. Parenting behavior and the parent-child relationship may thus be promising targets for interventions with this group of children.