This study reports results of a randomized, controlled trial examining the efficacy of the Family Check-Up (FCU) initiated during kindergarten on teacher report of children's emotional and behavior problems in first grade. Children's emotional and behavior needs at pretest were examined as a moderator. Participants were primary caregivers and teachers of 365 children in early elementary school. Using an intent-to-treat approach, results indicated children in the FCU condition outperformed children in a business-as-usual control condition on teacher report of emotional and behavior problems in first grade. Children experiencing higher levels of emotional and behavior problems at pretest benefited from the FCU more than did children who experienced lower levels of problems. Implications for family-centered interventions, study limitations, and future research directions are discussed. [This paper will be published in the "Journal of Emotional and Behavioral Disorders."]