This study examined the effectiveness of training Head Start teachers and aides in child teacher relationship training (CTRT). CTRT is based on child parent relationship therapy (CPRT) (Landreth & Bratton, 2006), a filial therapy model based on the principles of child-centered play therapy, and was adapted for the classroom. In this quasi-experimental design, 12 teacher/aide pairs (n = 24) were assigned to the experimental (n = 12) or active control group (n = 12). Children who scored in the Borderline or Clinical range on at least one scale of the Child Behavior Checklist-Caregiver/Teacher Report Form (C-TRF) at pretest qualified for the study (n = 54). Nine hypotheses were analyzed using a two factor repeated measures multivariate analysis to determine if the CTRT group and the active control group performed differently across time according to pre-, mid-, and posttest results of the C-TRF. Additionally, effect sizes were calculated to determine practical significance. Five hypotheses were retained at the .05 level of significance. Post hoc analysis was conducted to analyze the effects of the two phases of treatment. Results indicated that children in the experimental group made statistically significant improvements in externalizing problems (p = .003). Children of focus made statistically significant …