This study examines the role of one component of emotion regulation, behavioral control, in the growth of children's early behavior problems by examining whether increases in parental positive behavior support brought about by a family-centered intervention were associated with greater child behavioral control, and whether greater behavioral control at age 3 mediated the association between improvements in aspects of positive behavior support from ages 2 to 3 and decreases in growth of behavior problems from ages 2 to 4. The sample included 713 at-risk children (50% female) and their primary caregivers (50% European American, 28% African American, 13% biracial, 9% other) who were randomly assigned to the intervention or control group. Children had a mean age of 29.91 months at the initial assessment. Data were collected through home visits at child ages 2 to 4, which involved questionnaires for primary caregivers and structured and unstructured play activities for children with primary and alternative caregivers and siblings. Results indicated that the intervention improved parental positive behavior support and reduced growth of child behavior problems. One dimension of positive behavior support, proactive parenting, was modestly associated with behavioral control at age 3, which in turn was significantly associated with growth in behavior problems from ages 2 to 4, with greater behavioral control related to lower levels of growth in behavior problems. Results provide support for the notion that proactive parenting is an important factor in the development of children's behavioral control and that behavioral control plays an important role in the growth of behavior problems. (Contains 1 table, 3 figures and 1 footnote.)