Objective: We provide validation data on the Behavior Rating Inventory of Executive Functioning-Preschool version (BRIEF-P) in preschool children. Method: Teachers of a community sample of six hundred and twenty 3-year-olds, who were followed up at age 4, responded to the BRIEF-P, and parents and children answered different psychological measures. Results: Confirmatory factor analysis achieved adequate fit of the original structure (five-first-order-factor plus three-second-order-factor model) after excluding four items. The derived dimensions obtained satisfactory internal consistency, moderate convergent validity with psychopathology and temperament, and good ability to discriminate between children with ADHD. BRIEF-P scales were not associated with a performance-based measure of attention. The teacher’s BRIEF-P adds significant clinical information for the diagnosis of ADHD (DELTAR2 from 5.3 to 15.3) when used with other instruments for the assessment of psychopathology, functional impairment, or performance-based attention. Conclusion: The BRIEF-P may be useful in the identification of preschool children, specifically those with ADHD, who might have a dysfunction in executive functioning.