In this study, we examined the efficacy of a version of the Family Check-Up (FCU) adapted for kindergarten school entry with regard to parenting skills during the transition to school. We also examined whether improvements in parenting skills would mediate improvements in parent- and teacher-rated child behavior problems from kindergarten to second grade. The FCU is a motivational interviewing (MI) intervention designed to engage parents in treatment to improve parenting skills. Participants were parents of 365 children enrolled in one of five elementary schools in the Pacific Northwestern United States. Main and indirect effects were tested with structural equation path modeling using an intent-to-treat approach. The FCU was associated with improved change in parenting skills, and changes in parenting skills, in turn, predicted reductions in child behavior problems. Implications for embedding MI in family-centered interventions at kindergarten school entry are discussed. Trial registration: NCT02289092.