Head Start teachers and their aides (n = 24) were assigned to either the experimental or active control treatment in this preliminary investigation on the effects of Child Teacher Relationship Training (CTRT) on 52 disadvantaged preschool children identified with behavioral problems. CTRT is based on the principles and procedures of Child Parent Relationship Therapy (CPRT), a structured, time-limited approach that trains young children's caregivers to be active participants in an early mental health delivery system. Analysis of pre- to mid- to posttest findings revealed that, compared to the active control, CTRT demonstrated a large treatment effect on reducing children's externalized behavior problems; furthermore, the between-group difference over time was statistically significant. The statistical, practical, and clinical significance of findings provide preliminary support for CTRT as a developmentally responsive school-based intervention for at-risk preschool children exhibiting clinical levels of behavioral problems. © 2010 Wiley Periodicals, Inc.